Abstract:
A method for detecting a low-lift or zero-lift failure mode in a variable valve activation system of an internal combustion engine includes the steps of positioning a piezo-electric element that acts as a radio frequency transmitter relative to a lost motion spring of a two-mode variable valve activation lost motion device, subjecting the piezo-electric element to a compression load when a load from displacement of a lobe of a camshaft acts on the lost motion spring, broadcasting a radio frequency signal each time the piezo-electric element is subjected to the compression load, and evaluating the presence or absence of the broadcasted radio frequency signal in relation to an expected presence or absence of the radio frequency signal. The direct measurement of the mode of each two-mode device is both more reliable and more efficient in the use of engine controller resources compared to currently existing diagnostic methods.

Description:
TECHNICAL FIELD 
   The present invention relates to mechanisms for altering the actuation of valves in internal combustion engines; more particularly, to two-mode variable valve activation devices; and most particularly, to a method and apparatus for detection of a low-lift or zero-lift failure mode for such devices. 
   BACKGROUND OF THE INVENTION 
   Variable Valve Activation (VVA) mechanisms for internal combustion engines are well known. It is known to lower the lift, or even to provide no lift at all, of one or more valves of a multiple-cylinder engine, during periods of light engine load. Such deactivation or valve lift switching can substantially improve fuel efficiency. 
   Various approaches are known for changing the lift of valves in a running engine. One known approach is to provide an intermediary cam follower arrangement, which is rotatable about the engine camshaft and is capable of changing the valve lift and timing, the camshaft typically having both high-lift and low-lift lobes for each such valve. 
   For example, a Roller Finger Follower (RFF) typically acts between a rotating camshaft lobe and a pivot point such as a Hydraulic Lash Adjuster (HLA) to open and close an engine valve. By way of example, switchable deactivation RFF includes an outer arm, also known as body or low-lift follower, and an inner arm, also known as high-lift follower. The inner arm supports a roller carried by a shaft. The roller is engaged by a lobe of an engine camshaft that causes the outer arm to pivot about the HLA, thereby actuating an associated engine valve. The deactivation RFF is selectively switched between a coupled (high-lift) and decoupled (zero-lift) mode. In the coupled mode the inner arm is coupled to the outer arm by a movable latching mechanism and rotation of the lifting cam is transferred from the roller through the shaft to pivotal movement of the outer arm, which in turn, reciprocates the associated valve. In the decoupled mode, the inner arm is decoupled from the outer arm. Thus, the inner arm does not transfer rotation of the lifting cam lobe to pivotal movement of the outer arm, and the associated valve is not reciprocated. In this mode, the roller shaft is reciprocated within the outer arm. 
   A switchable, two-step RFF operates in a manner similar to the deactivation RFF, as described above. However, one particular difference between the operation of a deactivation RFF and a two-step RFF occurs in the decoupled mode of operation. When in the decoupled (zero-lift) mode, the outer arm of a deactivation RFF may be engaged by zero-lift cam lobes and remains in a static position allowing the associated valve to remain closed. On the other hand, when in decoupled (low-lift) mode, the outer arm of a two-step RFF is engaged by low-lift camshaft lobes to thereby reciprocate the associated engine valve according to the lift profile of the low-lift camshaft lobe. 
   A lost motion spring maintains contact between the roller and the lifting portion of the camshaft lobe when either type of RFF (i.e., deactivation or two-step) is in the decoupled (zero-lift or low-lift, respectively) mode and absorbs the reciprocal motion of the shaft and roller. The lost motion spring biases the inner arm away from the outer arm of the RFF. The expansion force of the lost motion spring acting on the inner arm must on the one hand be sufficient to maintain contact of the roller with the lifting portion of the cam lobe, while on the other hand must not cause the HLA, which supports the outer arm to be pumped down by the force of the lost motion spring. 
   Another known approach is to provide a deactivation mechanism in the Hydraulic Lash Adjuster (HLA) upon which a cam follower rocker arm pivots. Such arrangement is advantageous in that it can provide variable lift from a single cam lobe by making the HLA either competent or incompetent to transfer the motion of the cam eccentric to the valve stem. Yet another known approach is to provide a deactivation mechanism in the Hydraulic Valve Lifter (HVL). 
   During the operation of the above mentioned two-mode variable valve activation devices a variety of failure modes may occur. One failure mode of particular concern is the condition when one or more of the two-mode variable valve activation devices are stuck in the low-lift or zero-lift mode. This failure mode may have severe base-engine-level consequences at high engine speeds since the lost motion spring is only able to absorb the force provided by the lobe of the camshaft to the roller up to certain engine rotational speeds. Thus, extensive mechanical failure of the engine may occur if the engine is operated at high engine speeds in low-lift or zero-lift mode. Currently used passive diagnostic strategies that rely upon existing data available in engine management systems are in many cases neither responsive nor sensitive enough to satisfy customer requirements. The only alternative presently available is to compromise the camshaft profile to reduce valve closing velocity, thereby reducing the destructive energy associated with running the engine at high speeds in low-lift or zero-lift modes. This alternative is unacceptable because the resultant camshaft profile negates most of the potential fuel economy benefits achieved by applying two-mode VVA to the engine. This situation hampers the ability of the original equipment manufacturers to provide a two-mode VVA, a proven fuel economy and emissions improvement technology, in a federally certified production vehicle. 
   What is needed in the art is the ability to reliably detect a low-lift or zero-lift failure mode that occurs when one or more two-mode variable valve activation devices are stuck in low-lift mode at high engine speeds where these devices typically operate in high-lift mode. 
   It is a principal object of the present invention to provide a method and apparatus for direct measurement of the mode of each two-mode variable valve activation device used in a multiple-cylinder engine. 
   SUMMARY OF THE INVENTION 
   Briefly described, the invention addresses the shortcomings of prior art diagnostic strategies and algorithms for a low-lift or zero-lift failure mode of two-mode Variable Valve Activation (VVA) lost motion devices by integrating a piezo-electric Radio Frequency (RF) transmitter in each individual two-mode VVA device of a multiple-cylinder internal combustion engine. The direct measurement of the mode of each two-mode VVA device as opposed to the prior art attempts to infer the proper function of these devices by applying arcane neutral net or fuzzy logic data analysis techniques to existing engine control system data, is both more reliable and more efficient in it&#39;s use of engine controller resources, such as Random Access Memory (RAM), Read-only Memory (ROM), and throughput. The diagnostics in accordance with the invention is applicable for a variety of two-mode VVA lost motion devices, for example two-step and deactivation RFFs with compression or torsion lost motion springs, deactivation roller hydraulic valve lifters with internal or external lost motion springs, and deactivation switching Hydraulic Lash Adjusters (HLA). 
   The diagnostic strategy in accordance with the invention uses a wireless RF approach that employs an on-arm piezo-electric RF transmitter, for example in form of a piezo-electric wafer, and an under-camshaft cover RF receiver that is able to detect if one or more two-mode VVA devices are stuck in a low-lift or zero-lift mode. The piezo-electric RF transmitter is positioned preferably under the lost motion spring of each two-mode variable valve activation device. In one of the two operating modes of the VVA device, such as high-lift mode, one or more lock pins block the lost motion spring from being cyclically loaded by the camshaft lift displacement and, hence, no “lost motion” load is to be absorbed by the spring and, thus the piezo-electric transmitter. In this mode no RF transmission occurs. In the other of the two operating modes of the VVA device, such as low-lift or zero-lift mode, the lock pin or pins are retracted and the lost motion spring is subjected to the repetitive cyclical compression (or torsion) load from absorbing the displacement of the camshaft lobe or lobes. This cyclical load on the spring results in a compression load upon the piezo-electric transmitter. As a result of the compression load upon the piezo-electric transmitter an RF signal is transmitted with each cam lift event. Accordingly, the presence or absence of an RF signal in relation to an expected presence or absence of the RF signal can be used to reliably detect a malfunctioning two-mode VVA device. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will now be described, by way of example, with reference to the accompanying drawings, in which: 
       FIG. 1  is a cross-sectional view of a two-step roller finger follower assembly, in accordance with the invention; 
       FIG. 2  is a cross-sectional view of a first deactivation roller finger follower assembly, in accordance with the invention; 
       FIG. 3  is a side elevational view of a second deactivation roller finger follower assembly, in accordance with the invention; 
       FIGS. 4A and 4B  is a flow chart of piezo-electric diagnostics of a variable valve activation system utilizing two-mode roller finger follower assemblies, in accordance with the invention; 
       FIG. 5  is a cross-sectional view of a deactivation switching hydraulic lash adjuster assembly, in accordance with the present invention; 
       FIG. 6  is a cross-sectional view of a first deactivation roller hydraulic valve lifter assembly, in accordance with the invention; 
       FIG. 7  is a cross-sectional view of a second deactivation roller hydraulic valve lifter assembly, in accordance with the invention; and 
       FIGS. 8A and 8B  is a flow chart of piezo-electric diagnostics for cylinder deactivation, in accordance with the invention. 
   

   Corresponding reference characters indicate corresponding parts throughout the several views. The exemplification set out herein illustrates preferred embodiments of the invention, in one form, and such exemplification is not to be construed as limiting the scope of the invention in any manner. 
   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring to  FIG. 1 , a two-step Roller Finger Follower (RFF) assembly  100  includes an inner arm  102  that is pivotably disposed in an outer arm  104 . Inner arm  102  pivots within outer arm  104  about a pivot shaft  106 . A roller  108  for following a cam lobe  110  of a lifting cam of an engine camshaft  112  is carried by a shaft  114  that is supported by outer arm  102 . A socket  118  for pivotably mounting RFF assembly  100  on a Hydraulic Lash Adjuster (HLA)  120  is included at one end of outer arm  104 . A pad  122  for actuating a valve stem  124  is included at an opposite end of outer arm  104 . A latching mechanism  126 , such as lock pin  127 , disposed within outer arm  104  at the same end as socket  118  selectively couples or decouples inner arm  102  to or from outer arm  104 , which enables switching from a high-lift mode to a low-lift mode and vice versa. Controlled by an engine control module, pressurized oil supplied by the HLA  120  through oil passage  128  in known fashion hydraulically biases lock pin  126  from a retracted position to an expanded position toward inner arm  102 . When engine control module determines, in known fashion from various engine operating parameters, that inner arm  102  should be unlocked to switch to low-lift mode, the oil pressure is reduced such that a return spring  130  may bias lock pin  127  to a retracted position away from inner arm  102 . 
   A lost motion spring  140  acts between inner arm  102  and outer arm  104  by biasing inner arm  102  away from the outer arm  104  of the RFF. Lost motion spring  140  maintains contact between roller  108  and the lifting cam lobe  110  when RFF assembly  100  is in the decoupled mode. Lost motion spring  140  thus biases roller  108  against the lifting cam lobe  110 , and absorbs the reciprocal motion of shaft  114  and roller  108 . Lost motion spring  140  is shown in  FIG. 1  as a compression spring but may further be a torsion spring a shown in  FIG. 3 . RFF assembly  100  is a two-mode lost motion Variable Valve Activation (VVA) device. 
   A device that generates an electrical potential in response to an applied mechanical stress such as, for example, a piezo-electric element  150  is positioned under lost motion spring  140  such that a load from absorbing the displacement of the cam lobe  110  acting on lost motion spring  140  results in a compression load upon piezo-electric element  150 . Piezo-electric element  150  may be a wafer that may have a variety of geometric shapes. Piezo-electric element  150  may be, for example, a disk, a rectangular plate, or a ring. When piezo-electric element  150  is a ring, oil passage through element  150  is enabled for lubricating purposes. Piezo-electric element  150  acts as an RF transmitter and, accordingly, an RF signal is transmitted each time lost motion spring  140  is subjected to a load, a compression load. The RF signal is detected by an RF receiver (not shown) that is connected with an engine controller. The RF receiver may be positioned, for example, under a camshaft cover. 
   When RFF assembly  100  is operated in low-lift mode, lost motion spring  140  is subjected to a repetitive cyclical load from absorbing the displacement of inner arm  102  relative to outer arm  104  which results in a cyclical compression load upon the piezo-electric element  150  from which an RF signal is broadcasted by the transmitter. When RFF assembly  100  is operated in high-lift mode, lock pin  127  is expanded and substantially blocks lost motion spring  140  from being cyclically loaded by the displacement of cam lobe  110 , hence no load is to be absorbed by spring  140  and no compression load acts upon piezo-electric element  150 . As a result, no RF signal is broadcasted by the transmitter. The presence or absence of the broadcasted RF signals in relation to the expected presence or absence of the RF signals is used for diagnostics of the VVA mechanism of RFF assembly  100 . 
   Referring to  FIG. 2 , a first deactivation RFF assembly  200  includes an inner arm  202  that is pivotably and therefore deactivateably in an outer arm  204 . Inner arm  202  pivots within outer arm  204  about a pivot shaft  206 . A roller  208  is carried by a shaft  214  that is supported by the inner arm  202 . A lost motion spring  240  acts between inner arm  202  and outer arm  204 . As shown in  FIG. 2 , lost motion spring  240  may be, but is not limited to, a compression spring. Also, lost motion spring  240  may include one or more lost motion springs as shown in  FIG. 2 . A socket  218  for pivotably mounting RFF assembly  200  on an HLA, such as HLA  120  as shown in  FIG. 1 , is included at one end of outer arm  204 . A pad  222  for actuating a valve stem, such as valve stem  124  as shown in  FIG. 1 , is included at an opposite end of outer arm  204 . A latching mechanism  226 , such as lock pin  227 , disposed within outer arm  204  selectively couples or decouples inner arm  202  to or from outer arm  204 . 
   The deactivation RFF assembly  200  is selectively switched between a coupled and a decoupled state. In the coupled state, inner arm  202  is coupled to outer arm  204 , and rotation of a lifting cam lobe  210  is transferred from roller  208  through shaft  214  to pivotal movement of outer arm  204  about the HLA which, in turn, reciprocates the associated valve (normal or high-lift mode). In the decoupled state, inner arm  202  is decoupled from outer arm  204  and reciprocates within outer arm  204  thereby applying a cyclical load to lost compressing lost motion spring  240 . Rotation of cam lobe  210  is not transferred to pivotal movement of outer arm  204 . Instead, its rotational movement is absorbed by lost motion spring  240 . RFF  100  assembly is a two-mode lost motion VVA device. 
   A piezo-electric element  250  that has similar characteristics as piezo-electric element  150  as described above in connection with  FIG. 1  is positioned under lost motion spring  240  such that a load from absorbing the displacement of the cam lobe  210  results in a compression load upon piezo-electric element  250 . 
   Referring to  FIG. 3 , a second deactivation RFF assembly  300  is similar to the first deactivation RFF assembly  200  except that assembly  300  includes a torsion spring as lost motion spring  340 . A piezo-electric element  350  that has similar characteristics as piezo-electric element  150  as described above in connection with  FIG. 1  is positioned under one of the ends  342  that anchor the torsion spring to outer arm  204 . That is, an RF signal is transmitted by piezo-electric element  150  each time the lost motion spring is subjected to a torsion load when the inner arm is in lost motion. 
   When deactivation RFF assemblies  200  and  300  as shown in  FIGS. 2 and 3  are operated in zero-lift mode, lost motion springs  240  and  340  are subjected to a repetitive cyclical load from absorbing the displacement of inner arm  202  relative to outer arm  204  which results in a compression load upon the piezo-electric elements  250  and  350  and an RF signal is broadcasted by the transmitter. When deactivation RFF assemblies  200  and  300  as shown in  FIGS. 2 and 3  are operated in high-lift mode, latching mechanism  226  is expanded and substantially blocks lost motion springs  240  and  340  from being cyclically loaded by the displacement of cam lobe  210 , hence no load is to be absorbed by springs  240  and  340  and no compression load acts upon piezo-electric elements  250  and  350 . As a result, no RF signal is broadcasted. The presence or absence of the broadcasted RF signals in relation to the expected presence or absence of the RF signals is used for diagnostics of the VVA mechanism of deactivation RFF assemblies  200  and  300 . 
   Referring to  FIG. 4 , piezo-electric diagnostics  400  for a two-mode VVA system  412  utilizing two-mode RFF assemblies, such as two-step RFF assembly  100  and deactivation RFF assemblies  200  and  300  as shown in  FIGS. 1 through 3 , respectively, includes a low-lift diagnostics loop  420  and a high-lift mode diagnostics loop  450  that are both integrated in a main diagnostics loop  410  of an engine management system of an internal combustion engine. Low-lift mode diagnostics loop  420  is activated when VVA system  412  is operated in low-lift or zero-lift mode and high-lift mode diagnostics loop  450  is activated when VVA system  412  is operated in high-lift mode. 
   If the RF receiver is active in low-lift mode diagnostics loop  420 , one or more piezo-electric elements, such as element  150 ,  250 , or  350  as shown in  FIGS. 1-3 , respectively, are active and transmit RF signals in a step  422  and, therefore, one or more of the two-mode RFF assemblies are operating in low-lift mode. It is assumed in a step  424  that all two-mode RFF assemblies are operating properly and operation of the engine presumes without changes. 
   If the RF receiver is not active in low-lift mode diagnostics loop  420 , no RF signals are transmitted in a step  432  when all lost motion springs are expected to be active. The engine controller determines in a step  434  that all two-mode RFF assemblies are operating in high-lift mode and concludes in a step  436  that VVA system  412  is operating wrongly at the system level. Fault counter logic that requires a certain number of failures before setting a fault flag is applied in a step  438 . In a following step  442 , VVA diagnostic is activated and the malfunction indicator light is turned on. 
   If the RF receiver is active in high-lift mode diagnostics loop  450 , one or more piezo-electric elements are loaded compressively and transmit RF signals in a step  452 . Therefore, one or more of the two-mode RFF assemblies are still operating in low-lift mode. The engine controller determines in a step  454  that VVA system  412  is operating wrongly. Fault counter logic that requires a certain number of failures before setting a fault flag is applied in a step  456 . The fault counter logic may be set to a relatively low number of occurrences due to the severity of consequences of this failure mode. VVA diagnostic is activated in a step  458  and the malfunction indicator light is turned on. In addition, an operating speed limit may be applied to protect the engine from an over-speed condition. 
   If the RF receiver is not active in high-lift mode diagnostics loop  450 , no RF signals are transmitted in a step  462  when no lost motion spring events are expected. It is assumed in a step  464  that all two-mode RFF assemblies are operating in high-lift mode as expected and operation of the engine presumes without changes. 
   Referring to  FIG. 5 , cylinder deactivation using a deactivation switching hydraulic lash adjuster assembly  500  is another example of a two-mode VVA mechanism. Deactivation switching hydraulic lash adjuster assembly  500  includes a latching mechanism  526 , such as the two lock pins  527  shown in  FIG. 5 , a lost motion spring  540 , and a piezo-electric element positioned adjacent to lost motion spring  540  and such that compression of one or more lost motion springs  540  results in a compression load upon piezo-electric element  550 . 
   As with the two-mode RFF assemblies  100 ,  200 , and  300  as shown in  FIGS. 1 through 3 , respectively, and as described above, when deactivation switching hydraulic lash adjuster assembly  500  is in normal or high-lift mode, latching mechanism  526  holds the two-piece device rigid, substantially blocking lost motion spring  540  and thus piezo-electric element from being compressively loaded, and no RF signal is transmitted. When latching mechanism  526  is disabled and lock pins  527  are moved out of the way by the engine control system, lost motion spring  540  and piezo-electric element  550 , receive the compressive loads resulting from absorbing the displacement of the camshaft lobe or lobes, resulting in the piezo-electric element being compressed and transmitting an RF signal. Presence or absence of this RF signal in relation to an expected presence or absence of the RF signal is utilized for diagnostics of the deactivation switching hydraulic lash adjuster assembly  500 . 
   Referring to  FIGS. 6 and 7 , a first deactivation roller hydraulic valve lifter assembly  600  including an external lost motion spring  640  and a second deactivation hydraulic valve lifter assembly  700  including an internal lost motion spring  740  as illustrated, respectively. Assembly  600  includes furthermore a latching mechanism  626  and a piezo-electric element  650  that is positioned adjacent to lost motion spring  640  and such that compression of lost motion spring  640  results in a compression load upon piezo-electric element  650 . Assembly  700  includes furthermore a latching mechanism  726  and a piezo-electric element  750  that is positioned adjacent to lost motion spring  740  and such that compression of lost motion spring  740  results in a compression load upon piezo-electric element  750 . Assemblies  600  and  700  function similar as the deactivation switching hydraulic lash adjuster assembly  500  described above and as shown in  FIG. 5 . 
   Referring to  FIG. 8 , piezo-electric diagnostics  800  for a cylinder deactivation system  812  utilizing lost motion deactivation HLA&#39;s or lifters, such as deactivation switching hydraulic lash adjuster assembly  500  and deactivation roller hydraulic valve lifter assemblies  600  and  700  as shown in  FIGS. 5 through 7 , respectively, includes a deactivation mode diagnostics loop  820  and a normal (non-deactivation) mode diagnostics loop  850  are both integrated in a main diagnostics loop  810  of an engine management system of an internal combustion engine. Deactivation mode diagnostics loop  820  is activated when cylinder deactivation system  812  is operated in a deactivation mode and normal mode diagnostics loop  850  is activated when cylinder deactivation system  812  is operated in a normal mode that is comparable to the high-lift mode as in  FIG. 4 . 
   If the RF receiver is active in deactivation mode diagnostics loop  820 , one or more piezo-electric elements, such as element  550 ,  650 , or  750  as shown in  FIGS. 5-7 , respectively, are active and transmit RF signals in a step  822  and, therefore, one or more of the deactivation HLA&#39;s or lifters are operating in deactivation mode where the associated valves are not opened. It is assumed in a step  824  that the cylinder deactivation system  812  is operating properly and operation of the engine presumes without changes. 
   If the RF receiver is not active in deactivation mode diagnostics loop  820 , none of the piezo-electric elements is active and no RF signals are transmitted in a step  832  when all lost motion springs are expected to be active. The engine controller determines in a step  834  that all deactivation HLA&#39;s or lifters are operating in high-lift mode and concludes in a step  836  that cylinder deactivation system  812  is operating wrongly at the system level. Fault counter logic that requires a certain number of failures before setting a fault flag is applied in a step  838 . In a following step  842 , VVA diagnostic is activated and the malfunction indicator light is turned on. 
   If the RF receiver is active in normal mode diagnostics loop  850 , one or more piezo-electric elements are loaded compressively and transmit RF signals in a step  852 . Therefore, one or more of the deactivation HLA&#39;s or lifters are still operating in deactivation mode. The engine controller determines in a step  854  that cylinder deactivation system  812  is operating wrongly. Fault counter logic that requires a certain number of failures before setting a fault flag is applied in a step  856 . The fault counter logic may be set to a relatively low number of occurrences due to the severity of consequences of this failure mode. VVA diagnostic is activated in a step  858  and the malfunction indicator light is turned on. In addition, an operating speed limit may be applied to protect the engine from an over-speed condition. 
   If the RF receiver is not active in normal mode diagnostics loop  850 , none of the piezo-electric elements is active, and no RF signals are transmitted in a step  862  when no lost motion spring events are expected. It is assumed in a step  864  that all deactivation HLA/s and lifters are operating in normal mode as expected and operation of the engine presumes without changes. 
   By utilizing the presence of absence of RF signals broadcasted by the piezo-electric elements, such as piezo-electric elements  150 ,  250 ,  350 ,  450 ,  650 , and  750  as shown in  FIGS. 1-7 , respectively, various levels of diagnosability are possible dependent upon the level of complexity of the electronic circuitry and software. A first level of diagnosability, as shown in  FIGS. 4 and 8 , is to detect if one or more two-mode VVA lost motion devices transmit an RF signal when all two-mode VVA devices of an engine are operated in high-lift mode and should be quiet. Such a malfunction may set a malfunction indicator light and the engine controller may then take the appropriate failure mode actions to protect the base engine hardware, such as limiting the engine speed. Precise determination of which cylinder or which VVA device is malfunctioning may be done by other related VVA diagnostic algorithms utilizing the existing engine sensor set typically included in the engine management system, as well as dealer service bay diagnostic tools. 
   A second level of diagnosability is the detection of when in the crank angle domain the RF signal is occurring, and performing a simple calculation to determine its relative position to the engine&#39;s firing order. This would permit the diagnostics algorithm to set a different malfunction code for each engine cylinder the malfunction is associated with. The final determination of exactly which two-mode VVA lost motion device is malfunctioning may be left for the dealer service bay. 
   A third level of diagnosability is applicable for engines having two or more “two-mode” intake valves or exhaust valves per cylinder. By using distinctively different geometry piezo-electric elements in the lost motion devices within a cylinder, a first lost motion device may be constructed to broadcast a signal characteristic, such as signal frequency, that is distinctively different from a signal characteristic broadcasted by a second lost motion device within that same cylinder. Thus, the RF radio receiver may be made to provide different output signals to distinguish between first and second lost motion devices within a single cylinder. This added level of discernment, combined with the crank-angle correlation of the RF signal events, enables the diagnostic not only to determine which cylinder has the malfunctioning two-mode VVA lost motion device, but also which device on which valve in that cylinder. Since camshaft bearing towers typically create asymmetrical packaging needs to the VVA devices, with the third level of diagnosability, it is relatively simple to add an error-proofing asymmetry to the first and second lost motion devices, with similar differences in the geometry or appearance of the unique piezo-electric element for each first and second lost motion device, in order to prevent confusion during the assembly of the components. 
   While the invention has been described by reference to various specific embodiments, it should be understood that numerous changes may be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the described embodiments, but will have full scope defined by the language of the following claims.