Abstract:
A device and method for fluid delivery in a continuously variable transmission that includes a valve assembly, configured to distribute a fluid, having a first position and a second position. A forward clutch, a reverse clutch, and a torque converter are connected to the valve assembly. The valve assembly in the first position regulates either the forward clutch or the reverse clutch and opens the torque converter. In the second position, the valve assembly closes the forward clutch or the reverse clutch and regulates the torque converter. A controller commands the valve assembly to the first position and detects if the valve assembly is stuck in the second position. The controller is able to detect the valve assembly stuck in the second position and attempt to unstuck it while the continuously variable transmission is in drive.

Description:
FIELD 
     The present invention relates to vehicle transmissions and more particularly to a diagnostic system for detecting a stuck valve in a continuously variable transmission. 
     BACKGROUND 
     Continuously variable transmissions (CVTs) present many advantages over the conventional automatic step gear transmission including efficiency gains and a reduction in mechanical complexity. The continuously variable transmission may utilize a torque converter and neutral idle and garage shift features. Transmission fluid can be used to fluidly couple various components of the CVT. 
     Multiplex devices, similar to a modified conventional combination of valve assemblies, may be used in the continuously variable transmission to route the transmission fluid to various components. An exemplary implementation of a multiplex device is illustrated in  FIGS. 1 ,  2 A,  2 B,  3 A, and  3 B, where an exemplary multiplex device transmission control is generally indicated by reference numeral  10 . The transmission control system  10  includes a multiplex device  12 , which is supplied the transmission fluid at a controllable pressure by a transmission pump  14 . It should be appreciated that the multiplex device  12  may be indirectly connected to the transmission pump  14  and this connection may vary considerably between transmission configurations. Furthermore, the multiplex device  12  directs transmission fluid to other components of the transmission control system  10  but does not attenuate the pressure of the transmission fluid beyond typical mechanical losses. 
     The multiplex device  12  is further connected to a multiplex control  16 , which selectively switches the multiplex device  12  between an on position  12   a  (shown in  FIGS. 2A and 2B ) and an off position  12   b  (shown in  FIGS. 3A and 3B ). The multiplex device  12  selectively delivers transmission fluid through four delivery paths. The first path is indicated by reference numeral  18 . The second, third, and fourth path are indicated by reference numerals  20 ,  22 , and  24 , respectively. It will be appreciated that the multiplex device  12  utilizes two of the four delivery paths in one position and then utilizes the other two delivery paths in the other position. For example, the multiplex device  12  in the on position  12   a  ( FIGS. 2A and 2B ) communicates fluid through the first delivery path  18  and third delivery path  22 . The multiplex device  12  in the off position  12   b  ( FIGS. 3A and 3B ) communicates fluid through the second delivery path  20  and the fourth delivery path  24 . 
     The NI/GS control valve  26  is actuated by a dual valve control  28 , which also actuates a torque converter clutch (TCC) control valve  30 . The dual control valve  28  is configured to actuate the NI/GS control valve  26  in a way opposite the TCC control valve  30 . More specifically, when the dual control valve  28  opens the NI/GS control valve  26  to a maximum position, the dual control valve  28  controls the TCC control valve  30  to a minimum position. When the dual control valve  28  controls the NI/GS control valve  26  to a minimum position, the dual control valve  28  opens the TCC control valve  30  to a maximum position. The maximum position, with respect to the NI/GS control valve  26  and the TCC control valve  30 , is defined as allowing maximum flow through the valves  26  and  30 , which necessarily means the fluid pressure is not attenuated as it travels from transmission pump  14  though the multiplex device  12  to the valves  26  and  30  except for typical mechanical losses. The minimum position, on the other hand, is defined as reducing or attenuating the pressure of the transmission fluid as it travels through the valves  26  and  30  when compared to the transmission fluid pressure experienced at the multiplexer device  12 . 
     The NI/GS control valve  26  is fluidly connected to a forward/reverse clutch  32 , which directs the transmission fluid to either a modified conventional forward clutch  34  or a modified conventional reverse clutch  36 . The forward clutch  34  and the reverse clutch  36  are components of the transmission  38 , which are connected to an engine  40 . When the transmission fluid is directed to the NI/GS control valve  26  that is in the maximum position, the forward/reverse valve  32  routes transmission fluid at a maximum pressure from the NI/GS Control Valve  26  to either the forward clutch  34  or the reverse clutch  36 . When the transmission fluid is directed to the NI/GS control valve  26  that is in the minimum position, the forward/reverse valve  32  routes transmission fluid at a minimum pressure from the NI/GS Control Valve  26  to either the forward clutch  34  or the reverse clutch  36 . When either the forward clutch  34  or the reverse clutch  36  receives transmission fluid at a maximum pressure, either the forward clutch  34  or the reverse clutch  36  locks. In contrast, when either the forward clutch  34  or the reverse clutch  36  receives transmission fluid at a minimum pressure, either the forward clutch  34  or the reverse clutch  36  opens. 
     Maximum pressure is defined as the transmission fluid pressure at a certain point within the control system  10  being about equal to the transmission fluid pressure experienced at the multiplexer device  12 , acknowledging typical mechanical losses. Minimum pressure is defined as the transmission fluid pressure at a certain point within the transmission control system  10  being reduced, when compared to the transmission fluid pressure experienced at the multiplexer device  12 . In the various embodiments, maximum transmission fluid pressure is about 290 psi (about 2000 kPa) and minimum fluid pressure is about 0.3 psi (about 2 kPa). Minimum pressure further refers to an adequate amount of transmission fluid pressure required to cool and maintain the particular component in the transmission but not necessarily control it. 
     The TCC control valve  30  is fluidly connected to a modified conventional torque converter clutch  42  (TCC  42 ). The TCC  42  is a component of the transmission  38 , which is connected to an engine  40 . When the transmission fluid is directed to the TCC Control Valve  30  that is in the maximum position, the TCC  42  receives transmission fluid at a maximum pressure from the TCC Control Valve  30 . It follows that when the TCC control valve  30  that is in the minimum position, the TCC  42  receives transmission fluid at a minimum pressure from the TCC Control Valve  30 . When the TCC  42  receives transmission fluid at a maximum pressure, the TCC  42  locks. A locked TCC  42  causes a torque converter (not shown) that is conventionally connected to the transmission  38  to lock, which means the torque converter does not slip or experiences very little slippage. In contrast, when the TCC  42  receives transmission fluid at a minimum pressure, TCC  42  opens, which causes the torque converter to slip. 
     Table 1 below indicates the various positions of the components of the transmission control system  10 , shown in seven exemplary modes. Each mode represents possible exemplary configurations associated with the multiplex drive  12 , the NI-GS control valve  26 , the forward-reverse valve  32 , the forward clutch  34 , and the reverse clutch  36 . The labels of Maximum and Minimum in the column labeled NI-GS control valve  26  are in reference to the definitions noted above. Bypassed is defined to mean that the transmission fluid does not flow to this component. As shown in  FIG. 2 , for example, when the multiplex device  12  is in the on position  12   a , no transmission fluid flows to the NI-GS control valve  26 . As such, the NI-GS control valve  26  is bypassed, as the transmission fluid flows directly from the multiplex device  12  to the forward/reverse clutch  32 . 
     
       
         
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                   
                   
                 NI-GS 
                   
                   
                   
               
               
                   
                 Multiplex 
                 control 
                 forward-reverse 
                 forward 
                 reverse 
               
               
                 Modes 
                 Device 
                 valve (26) 
                 valve (32) 
                 clutch (34) 
                 clutch (36) 
               
               
                   
               
             
             
               
                 0 
                 Off 
                 N/A 
                 No Forward 
                 Open 
                 Open 
               
               
                   
                 Position 
                   
                 No Reverse 
               
               
                 1 
                 Off 
                 Maximum 
                 Forward 
                 Locked 
                 Open 
               
               
                   
                 Position 
               
               
                 2 
                 Off 
                 Maximum 
                 Reverse 
                 Open 
                 Locked 
               
               
                   
                 Position 
               
               
                 3 
                 Off 
                 Minimum 
                 Forward 
                 Open 
                 Open 
               
               
                   
                 Position 
               
               
                 4 
                 Off 
                 Minimum 
                 Reverse 
                 Open 
                 Open 
               
               
                   
                 Position 
               
               
                 5 
                 On 
                 Bypassed 
                 Forward 
                 Locked 
                 Open 
               
               
                   
                 Position 
                 Minimum 
               
               
                 6 
                 On 
                 Bypassed 
                 Forward 
                 Locked 
                 Open 
               
               
                   
                 Position 
                 Maximum 
               
               
                   
               
             
          
         
       
     
     Table 2 below indicates the various positions of the components of the transmission control system  10 , shown in the same seven different modes. Each mode represents possible exemplary configurations associated with the multiplex device  12 , the TCC control valve  30 , and the TCC  42 . The labels of Maximum and Minimum in the column labeled TCC control valve  30  are in reference to the definitions noted above. Bypassed is defined to mean that the transmission fluid does not flow to this component. As shown in  FIG. 3 , for example, when the multiplex device  12  is in the off position  12   a , no transmission fluid flows to the TCC control valve  30 . As such, the TCC control valve  30  is bypassed, as the transmission fluid flows directly from the multiplex device  12  to the TCC  42 . 
     
       
         
               
               
               
               
             
           
               
                   
               
               
                   
                 Multiplex 
                 TCC control 
                   
               
               
                 Modes 
                 Device (12) 
                 valve (30) 
                 TCC (42) 
               
               
                   
               
             
             
               
                 0 
                 Off Position 
                 Bypassed 
                 Open 
               
               
                   
                   
                 Minimum 
               
               
                 1 
                 Off Position 
                 Bypassed 
                 Open 
               
               
                   
                   
                 Minimum 
               
               
                 2 
                 Off Position 
                 Bypassed 
                 Open 
               
               
                   
                   
                 Maximum 
               
               
                 3 
                 Off Position 
                 Bypassed 
                 Open 
               
               
                   
                   
                 Maximum 
               
               
                 4 
                 Off Position 
                 Bypassed 
                 Open 
               
               
                   
                   
                 Maximum 
               
               
                 5 
                 On Position 
                 Minimum 
                 Open 
               
               
                 6 
                 On Position 
                 Minimum 
                 Open 
               
               
                   
               
             
          
         
       
     
     With reference to  FIGS. 3A and 3B  and Tables 1 and 2, the multiplex device  12  is shown in the off position  12   b . Modes  1 - 4  in Tables 1 and 2 indicated possible configurations of the components of the transmission control system  10 . Mode  1  refers to the multiplex device  12  in the off position  12   b , the forward-reverse valve  32  in a forward position  32   a  ( FIG. 3A ), and the NI-GS control valve  26  in a maximum position. Mode  2  is identical to Mode  1  except the forward-reverse valve  32  is in a reverse position  32   b  ( FIG. 3B ). In mode  1  and  2 , there is no transmission fluid directed though the first and the third delivery path  18  and  22  and, therefore, no transmission fluid is directed to the TCC control valve  30 . Because the TCC control valve  30  is bypassed, transmission fluid is delivered directly from the multiplex device  12  at a minimum pressure to the TCC  42 . Because transmission fluid is directed to the NI-GS Control Valve  26  and then to either the forward clutch  34  or reverse clutch  36  (depending on the position of the forward/reverse valve  32 ), the NI-GS control valve  26  is able to regulate either the forward clutch  34  or reverse clutch  36  accordingly. 
     Mode  3  is identical to Mode  1  and Mode  4  is identical to Mode  2  except the NI-GS control valve  26  is in a minimum position in Mode  3  and Mode  4  . Because transmission fluid is directed to the NI-GS control valve  26  set to the minimum pressure, either the forward clutch  34  or reverse clutch  36  (depending on the position of the forward/reverse valve  32 ) will remain open. It will be appreciated that when the NI-GS control valve  26  moves from the maximum position to the minimum position, the TCC control valve  30  moves from the minimum position to the maximum position because the dual control valve  28  controls control the two valves  26  and  30  oppositely. 
     With reference to  FIGS. 2A and 2B  and Tables 1 and 2, the multiplex device  12  is shown in the on position  12   a . Modes  5  and  6  in Tables 1 and 2 indicated possible configurations of the components of the transmission control system  10 . Mode  5  refers to the multiplex device  12  in the on position  12   a , the forward-reverse valve  32  in a forward position  32   a  ( FIG. 2A ), and the NI-GS control valve  26  in a maximum position. In mode  5 , there is no transmission fluid directed though the second and the fourth delivery path  20  and  24  and, therefore, no transmission fluid is directed to the NI-GS control valve  26 . Because the NI-GS control valve  26  is bypassed, transmission fluid is delivered directly from the multiplex device  12  at a maximum pressure to the forward/reverse valve  32 . Because transmission fluid is directed to the TCC control valve  30  and then to the TCC  42 , the TCC Control Valve  30  is able to open or close the TCC  42  accordingly. 
     Mode  6  is identical to Mode  5  except the TCC control valve  30  is in a minimum position in Mode  6 . Because transmission fluid is directed to the TCC control valve  30  set to the minimum pressure, the TCC  42  will remain open. It will be appreciated that when the TCC control valve  30  moves from the maximum position to the minimum position, the NI-GS Control Valve  26  moves from the minimum position to the maximum position because the dual control valve  28  controls control the two valves  26  and  30  oppositely. 
     A neutral-idle feature may be incorporated into an automatic transmission. In this example, a vehicle (not shown) comes to a stop. After a pre-determined period of time, the automatic transmission may initiate the neutral idle feature. More specifically, while waiting at the stop a driver may have the vehicle in a forward gear with a brake pedal pressed so that the vehicle is in gear but stopped. At this point, the transmission control system  10  may be in Mode  1 ; such that, the forward clutch  34  is locked and the TCC  42  is open. In this case, if the driver were to release the brake the vehicle would move forward, as the vehicle remains in gear even though the vehicle is stopped. To increase the efficiency of the engine  40 , the transmission control system  10  may open the forward clutch  34  thus removing the load on the engine  40 , which in turn may reduce fuel consumption and increase engine and transmission life. 
     To open the forward clutch, the multiplex device  12  must be in the off position  12   b  ( FIGS. 3A and 3B ) and the NI/GS control valve  26  must be in the minimum position. Because the NI/GS control valve  26  and the TCC control valve  30  are controlled by the same dual control valve  28 , the TCC control valve  30  will be in the maximum position when the NI/GS control valve  26  is in the minimum position. If the multiplex device  12 , however, is stuck in the on position  12   a  ( FIGS. 2A and 2B ), and the transmission control system  10  initiates the neutral idle feature, there is a possibility that the engine  40  will stall. More specifically, the NI/GS control valve  26  will still move from the maximum position to the minimum position in the attempt to unlock the forward clutch  34 , which in turn forces the TCC control valve  30  from the minimum position to the maximum position. The multiplex device  12 , however, is stuck in the on position  12   a  ( FIGS. 2A and 2B ) and transmission fluid is directed to the TCC control valve now in the maximum position. This scenario results in the forward clutch  34  being locked and the TCC  42  switching from open to being locked. If this scenario occurs, the engine  40  may stall. 
     A garage-shift feature may also be incorporated into an automatic transmission. In this example, a vehicle (not shown) comes to a stop and places the automatic transmission in either neutral or park. At this point, the automatic transmission may initiate the garage-shift feature. More specifically, the driver will either turn the ignition off or place the automatic transmission back into a forward or reverse drive gear to continue driving. Upon placing the automatic transmission back into a drive gear from either park or neutral, the automatic transmission will slowly engage the forward or reverse clutch accordingly to provide a smooth transition from stopped to forward or reverse motion. Not using the garage-shift feature may result in less attenuated or less smooth transition to forward or reverse motion from a stand still. 
     When the vehicle is parked and the automatic transmission is in either park or neutral, the transmission control system  10  is in Mode  0 ; such that, the multiplex device  12  is in the off position ( FIG. 3A ), the forward clutch  34  and the reverse clutch  36  are open, and the TCC  42  is open. Now when the driver shifts into a drive gear, the forward clutch  34  or reverse clutch  36  is slowly closed, to provide a gradual transition to forward or reverse motion. To slowly close the forward or reverse clutch, the multiplex device  12  must be in the off position  12   b  ( FIGS. 3A and 3B ) and the NI/GS control valve  26  must be moved from the minimum position to the maximum position. Because the NI/GS control valve  26  and the TCC control valve  30  are controlled by the same dual control valve  28 , the TCC control valve will be move from the minimum position to the maximum position when the NI/GS control valve  26  moves to the minimum position. 
     If the multiplex device  12 , however, is stuck in the on position  12   a  ( FIGS. 2A and 2B ), and the transmission control system  10  initiates the garage shift feature, there is a possibility that the engine  40  will stall. More specifically, the NI/GS control valve  26  will still move from the minimum position to the maximum position in the attempt to gradually lock the forward clutch  34  or reverse clutch  36 . The forward clutch  34  or reverse clutch  36  must open first, which requires the NI/GS control valve  26  to move from a maximum position to a minimum position. The TCC control valve  30 , therefore, moves from the minimum position to the maximum position. If, however, the multiplex device  12  is stuck in the on position  12   a  ( FIGS. 2A and 2B ) and transmission fluid is directed to the TCC control valve now in the maximum position. This scenario results in the forward clutch  34  or reverse clutch  36  being locked and the TCC  42  switching from open to being locked. If this scenario occurs when the vehicle is at a stand still the engine may stall. 
     In some instances, as noted above, the multiplex device  12  remains stuck in an on position when otherwise commanded to return to the off position. This failure, if gone undetected, may cause engine stall. Previous implementations of the multiplex device diagnostic to detect the multiplex device stuck in the on position have been limited to running the diagnostic only when the vehicle is in a park or neutral range. Further, the previous diagnostic was limited to transmission temperatures below 80° C. 
     SUMMARY 
     A device and method for fluid delivery in a continuously variable transmission that includes a valve assembly, configured to distribute a fluid, having a first position and a second position. A forward clutch, a reverse clutch, and a torque converter are connected to the valve assembly. The valve assembly in the first position regulates either the forward clutch or the reverse clutch and opens the torque converter. In the second position, the valve assembly closes the forward clutch or the reverse clutch and regulates the torque converter. A controller commands the valve assembly to the first position and detects if the valve assembly is stuck in the second position. 
     In another feature, the controller pulses the valve assembly in the second position to free the valve assembly. 
     In still another feature, the controller detects slippage of the torque converter to determine if the valve assembly is stuck in the second position. 
     Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
         FIG. 1  is a functional block diagram of the multiplex device integrated with the automatic transmission constructed in accordance with the teachings of the present invention; 
         FIG. 2A  is a functional block diagram of the multiplex device of  FIG. 1  showing the multiplex device in the on position and the forward/reverse valve in the forward position; 
         FIG. 2B  is a functional block diagram of the multiplex device of  FIG. 1  showing the multiplex device in the on position and the forward/reverse valve in the reverse position; 
         FIG. 3A  is a functional block diagram of the multiplex device of  FIG. 1  showing the multiplex device in the off position and the forward/reverse valve in the forward position; 
         FIG. 3B  is a functional block diagram of the multiplex device of  FIG. 1  showing the multiplex device in the off position and the forward/reverse valve in the reverse position; 
         FIG. 4  is a flow chart representing a continuously variable transmission range determination module that detects a multiplex device stuck on in the diagnostic system; 
         FIG. 5  is a flow chart representing a park/neutral module of the diagnostic system of  FIG. 4 ; 
         FIG. 6  is a flow chart representing a drive module of the diagnostic system of  FIG. 4 ; 
         FIG. 7  is a flow chart representing a check valve module of the drive module of  FIG. 6 ; 
         FIG. 8  is a flow chart representing an enable check valve module of the check valve module of  FIG. 7 ; 
         FIG. 9  is a flow chart representing a stability check valve module of the check valve module of  FIG. 7 ; 
         FIG. 10  is a flow chart representing a check valve module of the check valve module of  FIG. 7 ; 
         FIG. 11  is a flow chart representing an unstuck valve module of the drive module of  FIG. 6 ; 
         FIG. 12  is a flow chart representing a stability unstuck valve module of the unstuck valve module of  FIG. 11 ; and 
         FIG. 13  is a flow chart representing an unstuck valve module of the unstuck valve module of  FIG. 11 . 
     
    
    
     DETAILED DESCRIPTION 
     The following description of the preferred embodiments is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. For purposes of clarity, the same reference numbers will be used in the drawings to identify similar elements. As used herein, the term module and/or device refers to an application specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) and memory that execute one or more software or firmware programs, a combinational logic circuit, or other suitable components that provide the described functionality 
     With reference to  FIGS. 4-13 , a diagnostic system and method for detecting a multiplex device stuck in a position is generally indicated by reference number  100 . With reference to  FIG. 4 , a continuously variable transmission (CVT) range determination module is generally indicated by reference number  102 . The CVT range determination module  102  can proceed to either a park neutral module generally indicated by reference number  104  as shown in  FIG. 5  or a drive module generally indicated by reference numeral  106  as shown in  FIG. 6 . The drive module  106  ( FIG. 6 ) can proceed to a check valve module generally indicated by reference numeral  108  as shown in  FIG. 7 . The check valve module  108  can proceed to either an enable check valve module generally indicated by reference numeral  110  as shown in  FIG. 8 , a stability check valve module generally indicated by reference numeral  112  as shown in  FIG. 9 , or a check valve module generally indicated by reference numeral  114  as shown in  FIG. 10 . With reference to  FIG. 6 , the drive module  106  can also proceed to an unstuck valve module generally indicated with reference numeral  116  as shown in  FIG. 11 . The unstuck valve module  116  can proceed to either a stability unstuck valve module generally indicated by reference numeral  118  as shown in  FIG. 12 , or an unstuck valve module generally indicated by reference numeral  120  as shown in  FIG. 13 . 
     With reference to  FIG. 4 , the CVT range determination module  102  begins with step  122 . In step  122 , it is determined if the CVT range equals either high, intermediate, or low. It will be appreciated that high, intermediate, or low refer to various forward drive ranges of the CVT, in contrast to either reverse, park, or neutral. In step  122 , if the CVT range is equal to either high, intermediate, or low, the CVT range determination module  102  proceeds to step  124 . 
     In step  124 , it is determined if the time since the CVT changed range is greater than or equal to, a certain amount of time equal to a stuck on park constant. If the time since the CVT changed range is greater than, or equal to the stuck on park constant the CVT range determination module  102  proceeds from step  124  to the drive module  106  as shown in  FIG. 6 . In step  124 , if the time since the CVT changed range is less than the stuck on park constant, the CVT range determination module  102  proceeds to the park/neutral module  104  as shown in  FIG. 5 . 
     It will be appreciated that for clarity purposes, the method  100  is depicted across  FIGS. 4-13 . To make transitions between the Figures more clear, the reference letters “A” though “I” are used to indicate a transition to another figure. As shown in  FIG. 4 , for example, step  104  refers to the park/neutral module  104  of  FIG. 5 . It will be further appreciated that step  104  in  FIG. 4  is merely a reference holder for the park/neutral module  104 , which is depicted in  FIG. 5 . 
     In step  122 , if the CVT range does not equal either high, intermediate, or low the CVT range determination module  102  proceeds to step  126 . In step  126 , if the CVT range equals either park or neutral the CVT range determination module  102  proceeds to the park/neutral module  104  as shown in  FIG. 5 . In step  126 , if the CVT range does not equal either park or neutral, the CVT range determination module  102  proceeds to step  128 . 
     In step  128 , if the CVT range equals reverse, the CVT range determination module  102  proceeds to step  130 . In step  130 , if the time since the CVT changed range is less than the stuck on part constant, the CVT range determination module  102  proceeds to the park/neutral module  104  as shown in  FIG. 5 . In step  130 , if the time since the CVT changed range is greater than, or equal to, the stuck on park constant, the CVT range determination module  102  ends. In step  128 , if the CVT range is not equal to reverse, the CVT range determination module  102  ends and re-loops, if applicable. 
     With reference to  FIG. 5 , the first step of the park/neutral module  104  is step  132 . In step  132 , it is determined if the system has been initialized. It will be appreciated that when the diagnostic system and method  100  initially enters the park/neutral module  104 , the system will be initialized. If this system has to be initialized the park/neutral module  104  proceeds from step  132  to step  134 . In step  134 , the system is reset. 
     In the various embodiments, the reset of the system entails setting the following timers to 0 seconds: Low slip timer, high slip timer, pulse pass timer, pulse fail timer, and pulse wait timer. Also reset in step  134  is the pulse counter, which is reset to 0 counts. In step  134 , the following variables are also set to their respective values: Stuck on drive is set to initialization, TCC override is set to false, selection override is set to false, line override is set to false, and stuck on park variable is set to check park. After the completion of step  134 , the park/neutral module  104  loops back to step  132 . Because the variable stuck on park is set to check park, step  132  determines the system has already been initialized and proceeds to step  136 . 
     In step  136  it is determined if the engine and the throttle are set at the proper settings and speeds. In the various embodiments, the following must be true for the park/neutral module  104  to proceed from step  136  to step  138 . In step  136 , it is determined if all of the following is true: (1) An engine speed variable is greater than or equal to a minimum engine speed constant, (2) engine speed derivative variable is greater than or equal to a minimum engine speed derivative constant, (3) a throttle position variable is less than or equal to a maximum park/neutral throttle constant, (4) the throttle position variable is less than or equal to the sum of a start up throttle constant and an offset constant, (5) a transmission output speed variable is less than or equal to a maximum park/neutral transmission output speed constant, and (6) a park/neutral performance counter is less than or equal to a maximum park/neutral performance counter constant. If all of the above statements are true, the park/neutral module  104  proceeds from step  136  to step  138 . If one or more of the above statements in step  136  are not true, the park/neutral module  104  proceeds to step  160 . 
     In step  138 , it is determined if the CVT is in range. The CVT is in range if either of the following two statements is true. Is (1) the CVT range equal to either park or neutral for more than an amount of time equal to a minimum park/neutral timer constant? Is (2) the CVT range equal to either high, intermediate, low, or reverse for less than a maximum drive timer constant? If either of those two statements are true, the park/neutral module  104  moves from step  138  to step  140 . If both statements are false, the park/neutral module  104  proceeds from step  138  to step  160 . 
     In step  140 , it is determined if system pressures are above a minimum. If an actual line pressure variable is greater than or equal to a minimum pressure constant for an amount of time equal to a minimum pressure timer constant, the park/neutral module  104  proceeds from step  140  to step  142 . If the actual line pressure variable is less than the minimum pressure constant for a minimum pressure timer constant, the park/neutral module  140  proceeds to step  160 . It will be appreciated that a temperature measurement may be used to determine transmission fluid pressure. 
     In step  142 , it is determined if CVT is in either park or neutral. If the CVT range equals either park or neutral, the park/neutral module  104  proceeds from step  142  to step  144 . If the CVT range is not in either park or neutral, the park/neutral module  104  proceeds from step  142  to step  146 . 
     In step  144 , TCC override is set to false. In the various embodiments, when the TCC override is set to false the TCC is not forced on. From step  144 , the park/neutral module  104  proceeds to step  148 . In step  146 , TCC override is set to true and PCA override pressure is set to a park/neutral pressure constant. TCC override forces a PCA pressure not to turn on the selection solenoid. When the PCA override pressure variable is set to park/neutral pressure constant, the multiplex device transmission control system  10  internal pressure is set equal to that of the park/neutral pressure constant. Upon completion of step  146 , the park/neutral module  104  proceeds to step  148 . 
     In step  148 , the park/neutral sample counter is incremented, the selection override variable is set to true, and the multiplex override enable variable is set to false. In the various embodiments, the park/neutral sample counter is a counter recording the number of times the park/neutral test  104  is performed. When the selection override is set to true, it indicates the method  10  will override the multiplexer control  16  to the position indicated by multiplexer override variable. As such, when the multiplexer override enable variable is set to false, it indicates the position to which the multiplexer control  16  will be overridden; such that false indicates off. Upon completion of step  148 , the park/neutral module  104  proceeds to step  150 . 
     In step  150 , it is determined if (1) the diagnostic TCC slip variable is less than or equal to a park/neutral fail slip constant. It is also determined if (2) the engine speed variable is less than or equal to a maximum engine speed constant. If both are true, step  150  proceeds to step  152 . If one or more are false, step  150  proceeds to step  154 . In step  152 , the park/neutral failed counter is incremented. From step  152 , the park/neutral module  104  proceeds to step  154 . 
     In step  154 , it is determined if (1) the diagnostic TCC slip variable is greater than or equal to park/neutral pass slip constant. It is also determined if (2) the engine speed variable is less than or equal to the maximum engine speed constant. If both are true, the park/neutral module  104  proceeds from step  154  to step  156 . If one or more are false, the park/neutral module  104  proceeds from step  154  to step  158 . In step  156 , the park/neutral pass counter is incremented. From step  156 , the park/neutral module  104  proceeds to step  158 . 
     In step  158 , it is determined if the park/neutral sample counter is greater than or equal to a maximum sample constant. If yes, the park/neutral module proceeds from step  158  to step  160 . If no, the park/neutral module  104  proceeds from step  158  back to step  132 , which in turn causes the park/neutral module  104  to begin again. 
     In step  160 , it is determined if the test failed because the multiplexer device  12  ( FIG. 1 ) is stuck in the on position. To determine a failure, it is determined if (1) the park/neutral sample counter is greater than or equal to a minimum sample constant. It is also determined if (2) the park/neutral fail counter is greater than or equal to a fail counter. The fail counter is determined by multiplying the park/neutral sample counter by a fail percentage. If one or more of the above determinations are false, the park/neutral module  104  proceeds from step  160  to step  162 . If both are true, the park/neutral module proceeds from step  160  to step  164 . 
     In step  162 , it is determined if (1) the park/neutral sample counter is greater than, or equal to, a minimum sample constant. It is also determined if (2) the park/neutral pass counter is greater or equal to a pass counter. The pass counter is computed by multiplying the park/neutral sample counter by a pass percentage. If one or more are false, the park neutral module  104  ends after step  162 . If both are true, the park/neutral module  104  proceeds from step  162  to step  166 . In step  166 , it is indicated that the test passed. In step  164 , it is indicated that the test failed. From either step  164  or step  166 , the park/neutral module  104  proceeds to step  168 . 
     In step  168 , the park/neutral module  104  logs the data from the tests and resets the counters. More specifically the TCC override variable the set to false. The selection override variable is set to false. The line override variable is set to false. The park/neutral sample counter is set to zero counts. The park/neutral pass counter and the park/neutral fail counter are set to zero counts. The park/neutral performance counter is incremented. From step  168 , the park/neutral module  104  ends. 
     With reference to  FIGS. 1 and 5 , it should be appreciated that the park/neutral module  104  is attempting to determine if the multiplex device  12  is stuck in the on position. If the CVT is in either park or neutral, per step  142 , the park/neutral module  104  will lock the TCC  42  per step  146 . If the multiplex device  12  is not stuck and therefore in the off position, the TCC  42  will not lock. If, however, the multiplex device  12  is stuck in the on position, the TCC  42  will lock. If the TCC is locked due to the multiplex device  12  being stuck in the on position, step  150  will determine that the torque converter slip is less than or equal to the park/neutral fail slip constant, which is due to TCC being locked. If that determination is made, the park/neutral fail counter is incremented as shown in step  152 . 
     As noted above, if the multiplex device  12  is not stuck and therefore in the off position, the torque converter will not lock. Even when the TCC control  30  is forced to the maximum position the TCC  42  will not close because the multiplex device  12  is in the off position. Because the multiplex device  12  is in the off position, the TCC control valve  30  is bypassed and the TCC  42  remains at a minimum pressure thus open. 
     With reference to  FIG. 6 , the drive module is generally indicated by reference numeral  106 . The first step the drive module  106  is step  200 . In step  200 , it is determined if an initialization needs to be performed. In the various embodiments, and initialization is always initially performed. If an initialization has not yet been performed the drive module  106  proceeds from step  200  to step  202 . If an initialization has already been performed, the drive module  106  proceeds from step  200  to step  210 . 
     In step  202 , the system is reset and counters are set to zero. More specifically, the TCC override enable variable is to set to false. The line override variable is set to false. The park/neutral pass counter, the park/neutral fail counter, and the park/neutral sample counter are set to zero counts. The stuck on park variable is set to initialization. From step  202 , the drive module  106  proceeds to step to  204 . 
     In step to  204 , it is determined if (1) the selection valve stuck variable is equal to true. It is also determined if (2) the P0742 to error code is active. If neither are true, the drive module  106  proceeds from step  204  to step  206 . If one or more are true, the drive module  106  proceeds from step  204  to step to  208 . In step  206 , the stuck on drive variable is set to enable check valve. In step  208 , the stuck on drive variable is set to stability unstuck valve. From step  206  or step  208 , the drive module  106  ends and reloops if applicable. 
     In step  210 , it is determined if the stuck on drive variable is set to enable check valve. If yes, the drive module  106  proceeds from step  210  to the check valve module  108 . If no, the drive module  106  proceeds from step  210  to step  212 . In step  212 , is determined if the stuck on drive variable is set to stability unstuck valve. If yes, the drive module  106  proceeds from step  212  to the unstuck valve module  116 . If no, the drive module  106  ends after step  212 . 
     With reference to  FIG. 7 , the check valve module is generally indicated by reference  108 . The check valve module begins with step  214 . In step  214 , it is determined if the stuck on drive variable is set to enable check valve. If yes, the check valve module  108  proceeds from step  214  to the enable check valve module  110 , as shown in  FIG. 8 . If no, the check valve module  108  proceeds from step  214  to step  216 . 
     In step  216 , it is determined if the stuck on drive variable is set to stability check valve. If yes, the check valve module  108  proceeds from step  216  to the stability check valve module  112 , as shown in  FIG. 9 . If no, the check valve module  108  proceeds from step  216  to step  218 . 
     In step  218 , is determined if the stuck on drive variable is set to check valve. If yes, the check valve module  108  proceeds from step  218  to the check valve module  114 , as shown in  FIG. 10 . If no, the check valve module  108  ends after step  218  and reloops if applicable. 
     With reference to  FIG. 8 , the enable check valve module is generally indicated by reference numeral  110 . The enable check valve module starts with step  220 . In step  220 , it is determined if: (1) TCC zero pressure variable is equal to false. If it is false, the enable check valve module  110  proceeds from step  220  to step  221 . In step  221 , the TCC zero pressure variable is set to false, which does not force the TCC pressure to zero. If step  220  is true, the enable check valve module  110  proceeds from step  220  to step  222 . In step  222 , it is determined if: (1) multiplex enabled solenoid status variable is set to off. It is also determined if (2) the drive performance counter is less than or equal to a drive performance maximum constant. If all two are true, the enable check valve module  110  proceeds from step  222  to step  224 . If one or more are false, the enable check valve module  110  ends after step  222  and reloops if applicable. 
     From step  222 , the enable check valve module  110  proceeds to step  224 . In step  224 , the stuck on drive variable is set to stability check valve. From step  224 , the enable check valve module  110  ends. 
     With reference to  FIG. 9 , the stability check valve module is generally indicated by reference numeral  112 . The stability check valve module  112  begins with step  226 . In step  226 , it is determined if the engine and the CVT parameters are stable. More specifically, it is determined if (1) the diagnostic torque stability variable is less than or equal to the torque stability maximum constant. It is determined if (2) a diagnostic throttle stability variable is less than or equal to a throttle stability maximum constant. It is determined if (3) a diagnostic slip stability variable is less than or equal to a slip stability maximum constant. It is determined if (4) a diagnostic ratio stability variable is less than or equal to the ratio stability maximum constant for an amount of time equal to the check stability timer minimum constant. If all four are true, the stability check valve module  112  proceeds from step  226  to step  228 . If one or more are false, the stability check valve module  112  proceeds from step  226  to step  230 . 
     In the various embodiments, the diagnostic torque stability variable, the diagnostic throttle stability variable, the diagnostic slip stability variable, and the diagnostic ratio stability variable are determined by measuring true values from the engine and the CVT and multiplying those values by a filtering constant. For example, the diagnostic torque stability variable is determined by multiplying the measurement of CVT engine torque with a torque stability filter constant. This filtering process is similar for the remaining three variables, as the filter constant is identical for the respective variables. 
     In step  228 , the stuck on drive variable is set to check valve. From step  228 , the stability check valve module  112  ends. In step  230 , it is determined if any engine or CVT variables are above maximum values. More specifically, it is determined if (1) the diagnostic torque stability variable is greater than the torque stability maximum constant. It is determined if (2) a diagnostic throttle stability variable is greater than a throttle stability maximum constant. It is determined if (3) a diagnostic slip stability variable is greater than a slip stability maximum constant. It is determined if (4) a diagnostic ratio stability variable is greater than the ratio stability maximum constant. If any of the four are true, the stability check valve module  112  proceeds from step  230  to step  232 . If all are false, the stability check valve module  112  proceeds from step  230  to step  234 . 
     In step  232 , the stuck on drive variable is set to stability check valve. From step  232 , the stability check valve module  112  ends. In step  234 , it is determined if the TCC mode variable is not equal to off. If the TCC mode is not equal to off, the stability check valve module  112  proceeds from step  234  to step  236 . If the TCC mode variable is equal to off, the stability check valve module  112  ends after step  234 . In step  236 , the stuck on drive variable is set to enable check valve. From step  236 , the stability check valve module  112  ends. 
     With reference to  FIG. 10 , the check valve module is generally indicated by reference numeral  114 . The check valve module  114  begins with step  240 . In step  240 , it is determined if the multiplexer enabled solenoid status variable is not equal to off. If the multiplexer enabled solenoid status variable is not equal to off, the check valve module  114  proceeds from step  240  to step  242 . In step  242 , the stuck on drive variable is set to enable check valve. From step  242 , the check valve module  114  proceeds to step  244 . In step  244 , the timers and variables are reset. More specifically, the TCC override enable variable is set to false. The selection valve stuck variable is set to false. The selection override variable is set to false. The low slip timer is set to zero seconds and the high slip timer is set to zero seconds. From step  244 , the check valve module  114  ends. 
     In step  240 , if the multiplexer enabled solenoid status variable is equal to off, the check valve module  114  proceeds from step  240  to step  246 . In step  246 , it is determined if any engine variables are above maximum values. More specifically, it is determined if (1) the diagnostic torque stability variable is greater than the torque stability maximum constant. It is determined if (2) a diagnostic throttle stability variable is greater than a throttle stability maximum constant. It is determined if (3) a diagnostic ratio stability variable is greater than the ratio stability maximum constant. If any of the three are true, the check valve module  114  proceeds from step  246  to step  248 . If all are false, the check valve module  114  proceeds from step  246  to step  250 . In step  248 , the stuck on drive variable is set to stability check valve. From step  248 , the check valve module  114  proceeds to step  244 , as discussed above, where the timers and variables are reset. From step  244 , the check valve module  114  ends. 
     In step  250 , it is determined if (1) the transmission output speed variable is less than or equal to a maximum transmission output speed constant. It is also determined if (2) if the throttle position variable is greater than a maximum check throttle constant. If one or more are true, the check valve module  114  proceeds from step  250  to step  244 . If both are false, the check valve module  114  proceeds from step  250  to step  252 . 
     In step  244 , as discussed above, the timers and variables are reset. From step  244 , the check valve module  114  ends. In step  252 , the TCC override enable variable is set to true and TCC PCA override variable is set to a check pressure constant. From step  252 , the check valve module  114  proceeds to step  254 . 
     In step  254 , it is determined if the torque converter slip is less than or equal to a maximum check fail slip constant. If the torque converter slip is less than or equal to a maximum check fail slip constant, the check valve module proceeds from step  254  to step  256 . If the torque converter slip is greater than a maximum check fail slip constant, the check valve module proceeds from step  254  to step  262 . 
     In step  256 , the low slip timer is incremented and the high slip timer is reset to zero. From step  256 , the check valve module  114  proceeds to step  258 . In step  258 , it is determined if the low slip timer is greater than or equal to a fail timer. If no, the check valve module  114  ends after step  258 . If yes, the check valve module  114  proceeds from step  258  to step  260 . In step  260 , the selection valve stuck variable is set to true and the stuck on drive variable is set to stability unstuck valve. From step  260 , the check valve module  114  proceeds to step  268 . 
     In step  262 , the low slip timer is reset and high slip timer is incremented. From step  262 , the check valve module  114  proceeds to step  264 . In step  264 , it is determined if the high slip timer is greater or equal to a pass timer constant. If no, the check valve module  114  ends after step  264 . If yes, the check valve module  114  proceeds from step  264  to step  266 . In step  266 , a test pass indicator is set. Also in step  266 , the selection valve stuck variable is set to false, the driver performance counter is incremented, and the stuck on drive variable is set to enable check valve. From step  266 , the check valve module  114  proceeds to step  268 . 
     In step  268 , the TCC override enable variable is set to false and both the low slip timer and the high slip timer are set to zero seconds. From step  268 , the check valve module  114  ends and reloops if applicable. It will be appreciated that the check valve module  108  ( FIG. 7 ) performs the enable check valve module  110  ( FIG. 8 ) first and then the stability check valve module  112  ( FIG. 9 ) next, followed by the check valve module  114  ( FIG. 10 ). It will also be appreciated that the enable check valve module  110  ( FIG. 8 ) initiates when the multiplexer control  16  ( FIG. 1 ) is in the off position and will continue to loop until the test pass flag is set or until the maximum number of tests are reached per step  220  in  FIG. 8 . 
     After the enable check valve module  110  ( FIG. 8 ) is complete, the check valve module  108  ( FIG. 7 ) initiates the stability check valve module  112  ( FIG. 9 ) to detect variations in the four engine and CVT parameters. More specifically, the stability check valve module  112  ( FIG. 9 ) controls torque converter slippage, throttle position, engine torque, and gear ratio to determine if the engine and the CVT are stable enough to proceed to the check valve module  114  ( FIG. 10 ). The check valve module  114  ( FIG. 10 ) controls a certain pressure to the multiplexer  12  ( FIG. 1 ) to see if TCC  42  will close to thus lock the torque converter. If the multiplexer  12  ( FIG. 1 ) is not stuck, the change in pressure will not affect the TCC  42  ( FIG. 1 ). If the multiplexer  12  ( FIG. 1 ) is stuck on, such that the multiplexer  12  ( FIG. 1 ) remains in the on position ( FIGS. 2A and 2B ) while the multiplexer control  16  ( FIG. 1 ) is in the off position, the TCC  42  ( FIG. 1 ) will begin to close locking the torque converter in response to the change in pressure, thus detecting the multiplexer  12  ( FIG. 1 ) stuck on. If it is detected that the multiplexer  12  ( FIG. 1 ) is stuck on, the drive module  106  ( FIG. 6 ) proceeds to the unstuck valve module  116 , as shown in  FIG. 11 . 
     With reference to  FIG. 11 , the unstuck valve module is generally indicated by reference numeral  116 . The first step in the unstuck valve module  116  is step  300 . In step  300 , it is determined if the stuck on drive variable is set to stability unstuck valve. If yes, the unstuck valve module  116  proceeds from step  300  to the stability unstuck valve module  118 , as shown in  FIG. 12 . If no, the unstuck valve module  116  proceeds from step  300  to step  302 . In step  302 , it is determined if the stuck on drive variable is set to unstuck valve. If yes, the unstuck valve module  116  proceeds from step  302  to the unstuck valve module  120 , as shown in  FIG. 13 . If no, the unstuck valve module  116  ends after step  302 . 
     With reference to  FIG. 12 , the stability unstuck valve module is generally indicated by reference numeral  118 . The first step in the stability unstuck valve module  118  is step  304 . In step  304 , the TCC force on variable is set to true. From step  304 , the stability unstuck valve module  118  proceeds to step  306 . In step  306 , it is determined if the four engine and CVT parameters are above maximum values. More specifically, it is determined if (1) the diagnostic torque stability variable is less than or equal to the torque stability maximum constant. It is determined if (2) a diagnostic throttle stability variable less than or equal to the throttle stability maximum constant. It is determined if (3) the diagnostic slip stability variable less than or equal to the slip stability maximum constant. It is determined if (4) a diagnostic ratio stability variable less than or equal to the ratio stability maximum constant for an amount of time equal to the unstuck stability timer minimum constant. If any of the four are false, the stability unstuck valve module  118  proceeds from step  306  to step  308 . If all four are true, the stability unstuck valve module  118  proceeds from step  306  to step  310 . 
     In step  308 , the stuck on drive variable is set to unstuck valve and the stability unstuck valve module  118  ends. In step  310 , it is determined if (1) the diagnostic torque stability variable is greater than the torque stability maximum constant. It is determined if (2) a diagnostic throttle stability variable is greater than a throttle stability maximum constant. It is determined if (3) a diagnostic slip stability variable is greater than a slip stability maximum constant. It is determined if (4) a diagnostic ratio stability variable is greater than the ratio stability maximum constant. If all four are false, the stability unstuck valve module  118  ends after step  310 . If any of the four are true, the stability unstuck valve module  118  proceeds from step  310  to step  312 . In step  312 , the stability timer is reset. After step  312 , the stability unstuck valve module  118  ends. 
     With reference to  FIG. 13 , the unstuck valve module is generally indicated by reference numeral  120 . The first step in the unstuck valve module  120  is step  314 . In step  314 , it is determined if (1) the diagnostic torque stability variable is greater than the torque stability maximum constant. It is determined if (2) a diagnostic throttle stability variable is greater than a throttle stability maximum constant. If one or more are true, the unstuck valve module  120  proceeds from step  314  to step  316 . If both are false, the unstuck valve module  120  proceeds from step  314  to step  318 . 
     In step  316 , the selection override variable is set to false. The TCC override variable is set to false. The pulse pass timer, the pulse fail timer, and the pulse wait timer are set to zero seconds. The pulse counter is set to zero counts. The line override variable is set to false. The stuck on driver variable is set to stability unstuck valve. From step  316 , the unstuck valve module  120  ends. 
     In step  318 , it is determined if (1) the line override variable has been set to true for more than an amount of time equal to the pulse line timer constant. It is also determined if (2) the diagnostic slip stability variable is greater than the slip stability maximum constant. If both are true, the unstuck valve module  120  proceeds from step  318  to step  316  discussed above and then the unstuck valve module  120  ends after step  316 . If one or more are false, the unstuck valve module  120  proceeds from step  318  to step  320 . 
     In step  320 , it is determined if (1) the throttle position variable is less than or equal to an unstuck maximum throttle constant. It determined if (2) the transmission output speed variable is less than or equal to the maximum transmission output speed constant and greater than, or equal to, the minimum output transmission speed constant. It is determined if (3) the transmission line pressure less than or equal to the sum of a priority pressure constant minus an offset constant. It is determined if (4) the drive performance counter is less than or equal to the drive performance maximum constant. It is determined if (5) pulse performance variable is equal to false. If one or more are false, the unstuck valve module  120  proceeds from step  320  to step  322 . If all five are true, the unstuck valve module  120  proceeds from step  320  to step  326 . 
     In step  322 , it is determined if the transmission output speed variable is less than or equal to a transmission output speed maximum constant. If yes, the unstuck valve module  120  proceeds from step  322  to step  324 . If no, the unstuck valve module  120  proceeds from step  322  to  316  discussed above. In step  324 , the pulse performance variable is set to false. From step  324 , the unstuck valve module  120  proceeds to step  316 . From step  316 , the unstuck valve module  120  ends. 
     In step  326 , the line override variable is set to true, which results in a minimum transmission pressure. From step  326 , the unstuck valve module  120  proceeds to step  328 . In step  328 , it is determined if the line override variable is equal to true for a given amount of time equal to the line pulse timer. If no, the unstuck valve module  120  proceeds from step  328  ends. If yes, the unstuck valve module  120  proceeds from step  328  to step  330 . 
     In step  330 , the TCC override variable is set to true. The PCA override pressure variable is set to the lesser valve of either the sum of the PCA pressure constant plus an offset constant or the maximum pulse pressure constant. The selection override variable is set to true and multiplexer enabled override variable is set to false. From step  330 , the unstuck valve module  120  proceeds to step  332 . 
     In step  332 , it is determined if the absolute value of the torque converter slip variable is greater than or equal to the pass torque converter slip constant. If yes, the unstuck valve module  120  proceeds from step  332  to step  334 . If no, the unstuck valve module  120  proceeds from step  332  to step  336 . In step  334 , the pulse fail timer is reset and the pulse pass timer is incremented. From step  334 , the unstuck valve module  120  proceeds to step  336 . In step  336 , it is determined if the absolute value of the torque converter slip variable is less than or equal to the fail torque converter slip constant. If yes, the unstuck valve module  120  proceeds from step  336  to step  338 . If no, the unstuck valve module  120  proceeds from step  336  to step  340  and step  342 . In step  338 , the pulse fail timer is incremented and the pulse pass timer is reset. From step  338 , the unstuck valve module  120  proceeds to step  340  and step  342 . 
     In step  340 , it is determined if the pulse fail timer is greater than or equal to the fail timer constant. If no, the unstuck valve module  120  proceeds ends after step  340 . If yes, the unstuck valve module  120  proceeds from step  340  to step  344 . In step  342 , it is determined if the pulse pass timer greater than the pass timer constant. If no, the unstuck valve module  120  proceeds ends after step  342 . If yes, the unstuck valve module  120  proceeds from step  342  to step  346 . 
     In step  346 , the stuck on drive variable is set to enable check valve, the zero pressure variable is set to true, and the TCC force on variable is set to false. From step  346 , the unstuck valve module  120  proceeds to step  348 . In step  348 , the following variables are set to false: Valve stuck, TCC override, selection override, and line override. The following timers are set to zero seconds: Pulse pass timer, pulse wait timer, and pulse fail timer. The pulse counter is set to zero counts and the drive performance counter is incremented. From step  348 , the unstuck valve module  120  ends and reloops if applicable. 
     In step  344 , the TCC override variable and the selection override variable are set to false. The pulse pass, the pulse fail, and the pulse wait timers are set to zero seconds. The pulse counter is incremented. From step  344 , the unstuck valve module  120  proceeds to step  350 . In step  350 , it is determined if the pulse counter variable is greater than or equal to the maximum pulse constant. If yes, the unstuck valve module  120  proceeds from step  350  to step  352 . If no, the unstuck valve module  120  proceeds from step  350  to step  354 . 
     In step  352 , the test failed flag is set and the stuck on drive variable is set to unstuck valve. From step  352 , the unstuck valve module  120  proceeds back to step  348 , as discussed above. From step  348 , the unstuck valve module  120  ends. In step  354 , the pulse wait timer is incremented. From step  354 , the unstuck valve module  120  proceeds to step  356 . In step  356 , it is determined if the pulse wait timer is greater than or equal to wait timer constant. If no, the unstuck valve module  120  proceeds from step  356  back to step  354 . In step  354 , the pulse wait timer is incremented and the unstuck valve module proceeds back to step  356 . In step  356 , if the pulse wait timer is greater than or equal to wait timer constant, the unstuck valve module  120  ends. 
     It will be appreciated that the unstuck valve module  116  ( FIG. 11 ) begins with the stability unstuck valve module  118  ( FIG. 12 ), which is a similar engine and CVT stability criteria check to the stability check valve module  112 , as shown in  FIG. 9 . Once the stability criteria is satisfied, the unstuck valve module  116  ( FIG. 11 ) proceeds to the main portion of the module  116 , which is the unstuck valve module  120 , as shown in  FIG. 13 . The unstuck valve module  120  ( FIG. 13 ) determines whether to unstuck the multiplexer  12  ( FIG. 1 ) if it is stuck in the on position ( FIGS. 2A and 2B ). 
     Before the unstuck valve module  120  is performed the transmission must be at the appropriate output speed, which is between the transmission minimum output speed constant and the transmission maximum output speed constant. Also prior to performing the unstuck valve module  120  the vehicle must be in a coast condition, such that the throttle position is less than or equal to a unstuck maximum throttle position constant and the engine or CVT are not in a priority mode. In the various embodiments the priority modes refer to situations where engine and CVT control are governed by specific look-up tables. 
     With all of the specific criteria satisfied, the unstuck valve module  120  will pulse the multiplexer  12  ( FIG. 1 ) by turning off and turning on the multiplexer control  16  ( FIG. 1 ). After pulsing the multiplexer control  16  ( FIG. 1 ) a certain pressure is set in the multiplexer  12  ( FIG. 1 ) and the multiplexer control  16  ( FIG. 1 ) is set to off, which should move the multiplexer to the off position ( FIGS. 3A and 3B ) if it is not stuck. If the multiplexer device  12  ( FIG. 1 ) is stuck in the on position ( FIGS. 2A and 2B ), the TCC will begin to close. With the TCC  42  ( FIG. 1 ) closed and the torque converter locked, the unstuck valve module  120  will determine if the torque converter slippage is less than a fail threshold for at least a minimum amount of time. The unstuck valve module  120  will continue to poll torque converter slippage (or lack thereof) up to a maximum time. If threshold amount of slippage is not detected, the engine and CVT will set an error code to inform the driver that the vehicle needs service, as the multiplexer  12  ( FIG. 1 ) is stuck in the on position. 
     Those skilled in the art can now appreciate from the foregoing description that the broad teachings of the present invention can be implemented in a variety of forms. Therefore, while this invention has been described in connection with particular examples thereof, the true scope of the invention should not be so limited since other modifications will become apparent to the skilled practitioner upon a study of the drawings, the specification, and the following claims.