Abstract:
An electronically controlled engine management system for an outboard motor, which accurately checks the neutral switch for false operation. The accurate neutral switch detection permits an enjoyable boating environment as well as eliminating unnecessary false neutral switch fault alarms.

Description:
PRIORITY INFORMATION 
     This application is based on and claims priority to Japanese Patent Application No. 2001-136919, filed May 8, 2001 and to the Provisional Application No. 60/322,235, filed Sep. 13, 2001, the entire contents of which is hereby expressly incorporated by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to an engine control system for an outboard motor, and more particularly to an improved engine control system for determining if the neutral switch is faulty. 
     SUMMARY OF THE INVENTION 
     Watercraft engines typically incorporate an engine management system. Within the engine management system is commonly a neutral detection switch to prevent the engine from being started in either forward or reverse gear. Starting the engine in either forward or reverse gear permits a propeller to turn, possibly allowing for an unwanted movement of the watercraft as well as a hazard to anyone in the vicinity of the boat or boat propeller. 
     Under certain situations the engine management system may acquire data representing a false engine operating environment. In such situations a signal, for example from the neutral switch, may provide false information to the engine management system causing improper engine characteristics to be performed. 
     One aspect of the present invention is to be able to detect if the neutral switch is operating properly to consistently provide an accurate detection of the neutral position allowing for appropriate watercraft operation. Correct detection of a faulty neutral switch is favorable to the operator and the watercraft passengers as well as possible swimmers around the watercraft. 
     Another aspect of the present invention is to detect the operation of the neutral switch and accurately monitor and adjust engine parameters accordingly. Various components that can be adjusted in order to ensure proper engine performance depending on the status of the neutral switch may include the fuel injection and ignition. 
     Constant monitoring of various engine parameters is performed to control engine-running variables to allow the engine to correctly evaluate the status of the neutral switch and operate the engine correctly and efficiently under all conditions. The engine control system monitors the engine speed and determines whether a starting condition is present. During possible false starting conditions the engine management system ensures against false information from the neutral switch to provide the operator with a correct running engine. Such an advanced engine control system allows for correct, high performing engine life. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing features, aspects, and advantages of the present invention will now be described with reference to the drawings of a preferred embodiment that is intended to illustrate and not to limit the invention. The drawings comprise seven figures in which: 
     FIG. 1 is a side elevational view of an outboard motor configured in accordance with a preferred embodiment of the present invention, with an associated watercraft partially shown in section; 
     FIG. 2 is a side elevational view of an upper section of an outboard motor configured in accordance with a preferred embodiment of the present invention, with various parts shown in phantom; 
     FIG. 3 is a top view of an outboard motor configured in accordance with a preferred embodiment of the present invention, with various parts shown in phantom; 
     FIG. 4 is a schematic diagram of the electronic control unit and its control parameters; 
     FIG. 5 is a top view of a shifting cable mechanism, with various parts shown in phantom; 
     FIG. 6 is a graphical view showing engine parameters with reference to time; 
     FIG. 7 is a flowchart representing a control routine arranged and configured in accordance with certain features, aspects, and advantages of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The Overall Construction 
     With reference to FIGS. 1-5, an outboard motor  10  includes a drive unit  12  and a bracket assembly  14 . The bracket assembly  14  attaches the drive unit  12  to a transom  16  of an associated watercraft  18  and supports a marine propulsion device such as propeller  58  in a submerged position relative to a surface of a body of water. 
     As used to this description, the terms “forward,” “forwardly,” and “front” mean at or to the side where the bracket assembly  14  is located, unless indicated otherwise or otherwise readily apparent from the context use. The terms “rear,” “reverse,” “backwardly,” and “rearwardly” mean at or to the opposite side of the front side. 
     The illustrated drive unit  12  includes a power head  20  and the housing unit  22 . Unit  22  includes a drive shaft housing  24  and the lower unit  26 . The power head  20  is disposed atop the housing unit  22  and includes an internal combustion engine  28  within a protective cowling assembly  30 , which advantageously is made of plastic. The protective cowling assembly  30  typically defines a generally closed cavity  32  in which the engine  28  is disposed. The engine  28  is thereby is generally protected by the cowling assembly  30  from environmental elements. 
     The protective cowling assembly  30  includes a top cowling member  34  and a bottom cowling member  36 . The top cowling member  34  is advantageously detachably affixed to the bottom cowling member  36  by a suitable coupling mechanism to facilitate access to the engine and other related components. 
     The top cowling member  34  includes a rear intake opening (not shown) defined from an upper end portion. This rear intake member with one or more air ducts can, for example, be formed with, or affixed to, the top cowling member  34 . The rear intake member, together with the upper rear portion of the top cowling member  34 , generally defines a rear air intake space. Ambient air is drawn into the closed cavity  32  near the rear intake opening and the air ducts of the rear intake member. Typically, the top cowling member  34  tapers in girth toward its top surface, which is in the general proximity of the air intake opening. This taper reduces the lateral dimension of the outboard motor, which helps to reduce the air drag on the watercraft  18  during movement. 
     The bottom cowling member  36  has an opening for which an upper portion of an exhaust guide member  38  extends. The exhaust guide member  38  advantageously is made of aluminum alloy and is affixed to the top of the driveshaft housing  24 . The bottom cowling member  36  and the exhaust guide member  38  together generally form a tray. The engine  28  is placed on to this tray and can be connected to the exhaust guide member  38 . The exhaust guide member  38  also defines an exhaust discharge passage through which burnt charges (e.g., exhaust gases) from the engine  28  pass. 
     The engine  28  in the illustrated embodiment preferably operates on a four-cycle combustion principle. With reference now to FIGS. 2 and 3, the engine embodiment illustrated is a DOHC six-cylinder engine having a V-shaped cylinder block  40 . The cylinder block  40  thus defines two cylinder banks, which extend generally side by side with each other. In the illustrated arrangement, each cylinder bank has three cylinder bores such that the cylinder block  40  has six cylinder bores in total. The cylinder bores of each bank extend generally horizontally and are generally vertically spaced from one another. This type of engine, however, merely exemplifies one type of engine. Engines having other numbers of cylinders, having other cylinder arrangements (in line, opposing, etc.), and operating on other combustion principles (e.g., crankcase compression, two-stroke or rotary) can be used in other embodiments. 
     As used in this description, the term “horizontally” means that members or components extend generally and parallel to the water surface (i.e., generally normal to the direction of gravity) when the associated watercraft  18  is substantially stationary with respect to the water surface and when the drive unit  12  is not tilted (i.e., as shown in FIG.  1 ). The term “vertically” in turn means that proportions, members or components extend generally normal to those that extend horizontally. 
     A movable member, such as a reciprocating piston, moves relative to the cylinder block  40  in a suitable manner. In the illustrated arrangement, a piston (not shown) reciprocates within each cylinder bore. Because the cylinder block  40  is split into the two cylinder banks, each cylinder bank extends outward at an angle to an independent first end in the illustrated arrangement. A pair of cylinder head members  42  are fixed to the respective first ends of the cylinder banks to close those ends of the cylinder bores. The cylinder head members  42  together with the associated pistons and cylinder bores provide six combustion chambers (not shown). Of course, the number of combustion chambers can vary, as indicated above. Each of the cylinder head members  42  is covered with the cylinder head cover member  44 . 
     A crankcase member  46  is coupled with the cylinder block  40  and a crankcase cover member  48  is further coupled with a crankcase member  46 . The crankcase member  46  and a crankcase cover member  48  close the other end of the cylinder bores and, together with the cylinder block  40 , define the crankcase chamber. Crankshaft  50  extends generally vertically through the crankcase chamber and journaled for rotation about a rotational axis by several bearing blocks. Connecting rods couple the crankshaft  50  with the respective pistons in any suitable manner. Thus, a reciprocal movement of the pistons rotates the crankshaft  50 . 
     With reference again to FIG. 1, the driveshaft housing  24  depends from the power head  20  to support a drive shaft  52 , which is coupled with crankshaft  50  and which extends generally vertically through driveshaft housing  24 . The driveshaft  52  is journaled for rotation and is driven by the crankshaft  50 . 
     The lower unit  26  depends from the driveshaft housing  24  and supports a propulsion shaft  54  that is driven by the driveshaft  52  through a transmission unit  56 . A propulsion device is attached to the propulsion shaft  54 . In the illustrated arrangement, the propulsion device is the propeller  58  that is fixed to the transmission unit  56 . The propulsion device, however, can take the form of a dual counter-rotating system, a hydrodynamic jet, or any of a number of other suitable propulsion devices. 
     Preferably, at least three major engine portions  40 ,  42 ,  44 ,  46 , and  48  are made of aluminum alloy. In some arrangements, the cylinder head cover members  44  can be unitarily formed with the respective cylinder members  42 . Also, the crankcase cover member  48  can be unitarily formed with the crankcase member  46 . 
     The engine  28  also comprises an air intake system  72 . The air intake system  72  draws air from within the cavity  32  to the combustion chambers. The air intake system  72  shown comprises six intake passages  74  and a pair of plenum chambers  76 . In the illustrated arrangement, each cylinder bank communicates with three intake passages  74  and one plenum chamber  76 . 
     The most downstream portions of the intake passages  74  are defined within the cylinder head member  42  as inner intake passages. The inner intake passages communicate with the combustion chambers through intake ports, which are formed at inner surfaces of the cylinder head members  42 . Typically, each of the combustion chambers has one or more intake ports. Intake valves are slidably disposed at each cylinder head member  42  to move between an open position and a closed position. As such, the valves act to open and close the ports to control the flow of air into the combustion chamber. Biasing members, such as springs, are used to urge the intake valves toward their respective closed positions by acting between a mounting boss formed on each cylinder head member  42  and a corresponding retainer that is affixed to each of the valves. When each intake valve is in the open position, the inner intake passage thus associated with the intake port communicates with the associated combustion chamber. 
     Other portions of the intake passages  74 , which are disposed outside of the cylinder head members  42 , preferably are defined with intake conduits  78 . In the illustrated arrangement, each intake conduit  78  is formed with two pieces. One piece is a throttle body  80 , in which a throttle valve assembly  82  is positioned. Throttle valve assemblies  68  are schematically illustrated in FIG.  2 . The throttle bodies  80  are connected to the inner intake passages. Another piece is an intake runner  84  disposed upstream of the throttle body  80 . The respective intake conduit  78  extends forwardly alongside surfaces of the engine  28  on both the port side and the starboard side from the respective cylinder head members  42  to the front of the crankcase cover member  48 . The intake conduits  78  on the same side extend generally and parallel to each other and are vertically spaced apart from one another. 
     Each throttle valve assembly  82  preferably includes a throttle valve. Preferably, the throttle valves are butterfly valves that have valve shafts journaled for pivotal movement about generally vertical axis. In some arrangements, the valve shafts are linked together and are connected to a control linkage. The control linkage is connected to an operational member, such as a throttle lever, that is provided on the watercraft or otherwise proximate the operator of the watercraft  18 . The operator can control the opening degree of the throttle valves in accordance with operator request through the control linkage. That is, the throttle valve assembly  82  can measure or regulate amounts of air that flow through intake passages  74  through the combustion chambers in response to the operation of the operational member by the operator. Normally, the greater the opening degree, the higher the rate of airflow and the higher the engine speed. A throttle valve position sensor  86  measures the throttle valve opening position. The throttle valve position sensor  86  reflects the load requested by the operator and allows an electronic control unit  88  to calculate a signal used by fuel injectors  90  to inject the correct amount of fuel. A manifold pressure sensor  92  measures the pressure in the intake system  72  after the throttle valve assembly  82 . this measured pressure reflects the actual load of the engine and is likewise used by the ECU  88  to calculate the signal used by the fuel injectors  90 . 
     The respective plenum chambers  76  are connected with each other through one or more connecting pipes  94  (FIG. 3) to substantially equalize the internal pressures within each chamber  76 . The plenum chambers  76  coordinate or smooth air delivered to each intake passage  74  and also act as silencers to reduce intake noise. 
     The air within the closed cavity  32  is drawn into the plenum chamber  76 . The air expands within the plenum chamber  76  to reduce pulsations and then enters the outer intake passages  74 . The air passes through the outer intake passage  74  and flows into the inner intake passages. The throttle valve assembly  82  measures the level of airflow before the air enters into the inner intake passages. 
     The engine  28  further includes an exhaust system that routes burnt charges, i.e., exhaust gases, to a location outside of the outboard motor  10 . Each cylinder head member  42  defines a set of inner exhaust passages that communicate with the combustion chambers to one or more exhaust ports which may be defined at the inner surfaces of the respective cylinder head members  42 . The exhaust ports can be selectively opened and closed by exhaust valves. The construction of each exhaust valve and the arrangement of the exhaust valves are substantially the same as the intake valve and the arrangement thereof, respectively. Thus, further description of these components is deemed unnecessary. 
     Exhaust manifolds preferably are defined generally vertically with the cylinder block  40  between the cylinder bores of both the cylinder banks. The exhaust manifolds communicate with the combustion chambers through the inner exhaust passages and the exhaust ports to collect the exhaust gas therefrom. The exhaust manifolds are coupled with the exhaust discharge passage of the exhaust guide member  38 . When the exhaust ports are opened, the combustion chambers communicate with the exhaust discharge passage through the exhaust manifolds. A valve cam mechanism preferably is provided for actuating the intake and exhaust valves in each cylinder bank. In the embodiment shown, the valve cam mechanism includes second rotatable members such as a pair of camshafts  96  per cylinder bank. The camshafts  96  typically comprise intake and exhaust camshafts that extend generally vertically and are journaled for rotation between the cylinder head members  42  and the cylinder head cover members  44 . The camshafts  96  have cam lobes (not shown) to push valve lifters that are fixed to the respective ends of the intake and exhaust valves in any suitable manner. Cam lobes repeatedly push the valve lifters in a timely manner, which is in proportion to the engine speed. The movement of the lifters generally is timed by rotation of the camshaft  96  to appropriately actuate the intake and exhaust valves. 
     A camshaft drive mechanism  98  preferably is provided for driving the valve cam mechanism. The camshaft drive mechanism  98  in the illustrated arrangement is formed above a top surface  100  (see FIG. 2) of the engine  28  and includes driven sprockets  80  positioned atop at least one of each pair of camshafts  96 , a drive sprocket  104  positioned atop the crankshaft  50  and the flexible transmitter, such as a timing belt or chain  106 , for instance, wound around the driven sprockets  102  and the drive sprocket  104 . The crankshaft  50  thus drives the respective camshafts  96  through the time belt  106  in the timed relationship. 
     The illustrated engine  28  further includes indirect, port or intake passage fuel injection. In one arrangement, the engine  28  comprises fuel injection and, in another arrangement, the engine  28  is carburated. The illustrated fuel injection system shown includes six fuel injectors  90  with one fuel injector allotted to each one of the respective combustion chambers. The fuel injectors  90  preferably are mounted on the throttle body  66  of the respective banks. 
     Each fuel injector  90  has advantageously an injection nozzle directed downstream within the associated intake passage  74 . The injection nozzle preferably is disposed downstream of the throttle valve assembly  82 . The fuel injectors  90  spray fuel into the intake passages  74  under control of the electronic control unit (ECU)  88  (FIG.  4 ). The ECU  88  controls the initiation, timing and the duration of the fuel injection cycle of the fuel injector  90  so that the nozzle spray a desired amount of fuel for each combustion cycle. 
     A vapor separator  108  preferably is in full communication with the tank and the fuel rails, and can be disposed along the conduits in one arrangement. The vapor separator  108  separates vapor from the fuel and can be mounted on the engine  28  at the side service of the port side. 
     The fuel injection system preferably employs at least two fuel pumps to deliver the fuel to the vapor separator  108  and to send out the fuel therefrom. More specifically, in the illustrated arrangement, a lower pressure pump  110 , which is affixed to the vapor separator  108 , pressurizes the fuel toward the vapor separator  108  and the high pressure pump (not shown), which is disposed within the vapor separator  108 , pressurizes the fuel passing out of the fuel separator  108 . 
     A vapor delivery conduit  112  couples the vapor separator  108  with at least one of the plenum chambers  76 . The vapor removed from the fuel supply by the vapor separator  108  thus can be delivered to the plenum chambers  76  for delivery to the combustion chambers with the combustion air. In other applications, the engine  28  can be provided with a ventilation system arranged to send lubricant vapor to the plenum chamber(s). In such applications, the fuel vapor also can be sent to the plenum chambers via the ventilation system. 
     The engine  28  further includes an ignition system including an ignition determination method  113 . Each combustion chamber is provided with a spark plug  114  (see FIG.  4 ), advantageously disposed between the intake and exhaust valves. Each spark plug  114  has electrodes that are exposed in the associated combustion chamber. The electrodes are spaced apart from each other by a small gap. The spark plugs  114  are connected to the ECU  88  through ignition coils  116 . Individual ignition coils  116  can control each spark plug  114  or each ignition coil  116  can control two spark plugs, firing them simultaneously. One or more ignition triggering sensors  118  are positioned around a flywheel assembly  120  to trigger the ignition coils, which in return trigger the spark plugs  114 . The spark plugs  114  generate a spark between the electrodes to ignite an air/fuel charge in the combustion chamber according to desired ignition timing maps or other forms of controls. 
     During engine starting, a starter  122  initiated by an engine starting method  123  can temporarily engage a starter gear  124  through a starter motor shaft  126  with a ring gear  128  attached to the flywheel assembly  120 . The starter  122  drives the engaged starter gear  124  to turn the flywheel assembly allowing the engine  28  to start. 
     Generally, during an intake stroke, air is drawn into the combustion chambers through the air intake passages  74  and fuel is mixed with the air by the fuel injectors  90 . The mixed air/fuel charge is introduced to the combustion chambers. The mixture is then compressed during the compression stroke. Just prior to a power stroke, the respective spark plugs ignite the compressed air/fuel charge in the respective combustion chambers. The air/fuel charge thus rapidly burns during the power stroke to move the pistons. The burnt charge, i.e., exhaust gases, then is discharged from the combustion chambers during an exhaust stroke. 
     The illustrated engine further comprises a lubrication system to lubricate the moving parts within the engine  28 . The lubrication system is a pressure fed system where the correct pressure is important to adequately lubricate the bearings and other rotating surfaces. The lubrication oil is taken from an oil reservoir  130  and delivered under pressure throughout the engine to lubricate the internal moving parts. 
     The flywheel assembly  120 , which is schematically illustrated with phantom line in FIG. 3, preferably is positioned atop the crankshaft  50  and is positioned for rotation with the crankshaft  50 . The flywheel assembly  120  advantageously includes a flywheel magneto for AC generator that supplies electric power directly or indirectly via a battery to various electrical components such as the fuel injection system, the ignition system and the ECU  88 . An engine cover  132  preferably extends over almost the entire engine  28 , including the flywheel assembly  120 . 
     In the embodiment of FIG. 1, the driveshaft housing  24  defines an internal section of the exhaust system that leaves the majority of the exhaust gases to the lower unit  26 . The internal section includes an idle discharge portion that extends from a main portion of the internal section to discharge idle exhaust gases directly to the atmosphere through a discharge port that is formed on a rear surface of the driveshaft housing  24 . 
     Lower unit  26  also defines an internal section of the exhaust system that is connected with the internal exhaust section of the driveshaft housing  24 . At engine speeds above idle, the exhaust gases are generally discharged to the body of water surrounding the outboard motor  10  through the internal sections and then a discharge section defined within the hub of the propeller  58 . 
     The engine  28  may include other systems, mechanisms, devices, accessories, and components other than those described above such as, for example, a cooling system. The crankshaft  50  through a flexible transmitter, such as timing belt  106  can directly or indirectly drive those systems, mechanisms, devices, accessories, and components. 
     The Engine Control System 
     Successful engine operation is desirable and requires accurate response and adjustments of the controlling engine parameters. Successful engine operation is dependent in part by a correctly operating neutral switch  134 . The present invention provides an engine control routine to accurately evaluate the condition of the neutral switch  134  while inhibiting an abnormal condition alarm when the engine is abruptly stopped. If the neutral switch  134  is found to be faulty, the control routine initiates a visual alarm  135  and an audible alarm  137  to warn the operator. 
     As seen in FIG. 5, the construction of the shift cable mechanism  64  is shown. A double sided arrow  136  represents the normal movement of the slider  70  within a guide groove  138  when either a forward gear position represented by F is selected or a reverse gear position represented by R is selected. When the slider  70  is positioned in the middle of the guide groove  138 , the neutral switch  134  is closed sending a respective signal to the ECU  88 . When, however the slider is in either the forward gear position or the reverse gear position, the neutral switch  134  is open sending a corresponding signal to the ECU  88 . 
     When an engaged forward or reverse gear is reluctant to disengage, for example while engine torque is being applied to the transmission, the force to move the slider  70  can be excessive. During such an excessive force movement of the slider  70 , the entire shift bracket  68  moves counter clockwise as shown by arrows  140 . The movement of the bracket  68  due to excessive shifting force opens an excessive shifting force switch  142 , sending a respective signal to the ECU  88 . 
     FIG. 6 represents a graph of various engine parameters showing the invention during a period when the ECU automatically detects if the neutral switch  134  is properly operating. Waveform  144  represents an ignition coil current. A point  146  represents the initiation of an ignition coil current timer, which occurs each time a current is applied to the ignition coils  116 . If the engine is abruptly stopped, after a predetermined time  148  has passed, the current to the ignition coils is automatically interrupted at a point  150  in order to prevent damage to the ignition coil. Such damage can result if the ignition coil current is allowed to continue after the engine is stopped. In one embodiment of the present invention, the predetermined time  148  can represent 1.28 seconds. The predetermined time  148  only reaches its time limit and interrupts the current to the ignition coils under the condition when the engine is turning at a speed less than 100 RPM. In some instances when the ignition coil current is interrupted, a firing of the corresponding spark plug  114  can occur. If the inadvertent firing of the spark plug  114  occurs when a piston within the engine  28  is just below top dead center during a compression stroke, the engine  28  can begin to turn in the false direction. A signal  152  on the graph represents the detection of the engine turning through an engine speed determination method  153 . This turning of the engine after the current to the ignition coils has been interrupted can represent a reverse turning of the engine  28 . Any detection from the ignition triggering sensors  118  ranging from a single pulse to a signal representing an engine speed of 500 RPM is translated by the ECU  88  as a starting mode. When the current to the ignition coils  116  is stopped, an abnormal engine rotation timer begins at point  154 . A predetermined amount of time  156  is allowed to pass in which the detection of a faulty neutral switch through an abnormality detection method or mode  157  is suspended. In one embodiment of the present invention, the predetermined amount of time can represent 800 milliseconds. The time period  152  compared to the time period  148  is presented in an exaggerated scale to illustrate the engine rotation signal  152 . As described below, this suspension of abnormality detection allows for correct determination of status of the neutral switch  134  and inhibits producing a false abnormal signal. 
     An engine speed signal  158  can be seen decreasing in value with time until it reaches an engine stop point  160 , which is determined by an engine stop determination method  161 . This engine stop point can be determined by the engine stop determination method  161  when an engine speed signal representing an engine speed less than 100 RPM is present. As can be seen in FIG. 6 the engine can start to turn in either direction when the current to the ignition coils has ceased. A signal  162  from the neutral switch  134  which is unchanged in the open position shows that the ECU  88  detects a start mode when the engine  28  falsely turns. The abnormality determination method of mode  157  does not accurately check the status of the neutral switch  134  during this false start mode period  156 . 
     FIG. 7 shows a control routine  166  implemented by ECU  88  arranged and configured in accordance with certain features, aspects, and advantages of the present invention. The control routine  166  begins and moves to a first operation block P 10  in which the ignition coil current timer is started. The control routine  166  then moves to decision block P 12 . 
     In decision block P 12 , it is determined if the engine has stopped; i.e., the RPM is less than 100. If in decision block P 12  the engine has not stopped the control routine  150  moves to operation block P 14 . If, however, in decision block P 12  it is determined that the engine has stopped, the control routine moves to decision block P 16 . 
     In operation block P 14 , the coil current timer is reset and normal operation is continued; i.e., the ignition coils receive a normal current. 
     In decision block P 16 , it is determined if the ignition coil current timer has exceeded at predetermined value. In decision block P 16  if the ignition coil current timer has not exceed a predetermined value, the control routine  166  returns to decision block P 12 . If, however, in decision block P 16  the ignition coil current timer has exceeded a predetermined value, the control routine  166  moves to operation block P 18 . 
     In operation block P 18 , current to the ignition coils is interrupted and the ignition coil current timer is reset. The control routine  166  then moves to operation block P 20 . 
     In operation block P 20 , a timer is started. This timer is set to time the period  156  to suspend detection of a faulty neutral switch during an abnormal engine rotation as described above. The control routine then moves to decision block P 22 . 
     In decision block P 22 , it is determined if at least one ignition trigger sensor has detected a signal. If in decision block P 22  it is determined that one ignition triggers sensor signal has not been detected, the control routine  166  moves to operation block P 30 . If, however, in decision block P 22  at least one ignition trigger sensor signal is detected, signaling engine rotation, the control routine moves the decision block P 24 . 
     In decision block P 24 , it is determined if the neutral switch is open. If the neutral switch is not open, the control routine moves to operation block P 30 . The neutral switch can only be determined to be open by the ECU when the slider  70  is in the forward position, the reverse position, or if there is a fault, e.g. an open circuit within the neutral switch or its wiring. If it is determined that the neutral switch is open, the control routine  166  moves to decision block P 26 . 
     In decision block P 26 , it is determined if an abnormal engine rotation timer has reached a predetermined value. If in decision block P 26  an abnormal engine rotation timer has not reached a predetermined value, the control routine  166  returns to decision block P 22 . If, however, in decision block P 26  the abnormal engine rotation timer has reached a predetermined value, the control routine moves to operation block P 28 . 
     In operation block P 28 , the control routine using the abnormality detection method or mode  157  described above, determines that the neutral switch is faulty. During a starting mode, e.g. at least one ignition trigger signal detected after the abnormal engine rotation timer has reached its predetermined value, the neutral switch must be closed in order for the ECU to initiate the starter. If it is determined that the engine  28  is in a starting mode, and the neutral switch is open, the neutral switch must be faulty. The visual alarm  135  and the audible alarm  137  are initiated to warn the operator. The control routine  166  moves to operation block P 30 . 
     In operation block P 30 , the abnormal engine rotation timer is reset. The control routine then returns. 
     It is to be noted that the control system described above may be in the form of a hard-wired feedback control circuit in some configurations. Alternatively, the control system may be constructed of a dedicated processor and memory for storing a computer program configured to perform the steps described above in the context of the flowchart. Additionally, the control systems may be constructed of a general-purpose computer having a general-purpose processor and memory for storing the computer program for performing the routine. Preferably, however, the control system is incorporated into the ECU  88 , in any of the above-mentioned forms. 
     Although the present invention has been described in terms of a certain preferred embodiments, other embodiments apparent to those of ordinary skill in the art also are within the scope of this invention. Thus, various changes and modifications may be made without departing from the spirit and scope of the invention. For instance, various steps within the routines may be combined, separated, or reordered. In addition, some of the indicators sensed (e.g., engine speed and throttle position) to determine certain operating conditions (e.g., rapid deceleration) can be replaced by other indicators of the same or similar operating conditions. Moreover, not all of the features, aspects and advantages are necessarily required to practice the present invention. Accordingly, the scope of the present invention is intended to be defined only by the claims that follow.