In order to detect an engine misfire at higher engine speeds, the Powertrain Control Module (PCM) must know of any variation between the crankshaft sensor pulses. Most variations are due to the machining of the crankshaft reluctor wheel, however, other sources of variation are also possible. A crankshaft position system variation learn procedure must be performed any time that you perform the following service procedures, regardless of whether or not the DTC P1336 is set:

The PCM measures the variations and then calculates compensation factors needed in order to enable the PCM to accurately detect an engine misfire at all speeds and loads. A scan tool must be used to command the PCM to learn these variations. A DTC P1336 will set if the PCM has not had the crankshaft position system variation learn procedure performed due to replacement or a reprogramming.

Caution: Before performing the Crankshaft Position System Variation Learning Procedure always set the vehicle parking brake and block the drive wheels in order to prevent personal injury. Release the throttle immediately when the engine starts to decelerate in order to eliminate over revving the engine. Once the learn procedure is completed, the control module will return engine control to the operator and the engine will respond to the throttle position.

DTC P1336 will only set if the PCM has not learned the crankshaft position system variation. The PCM only needs to learn this variation once per life cycle of the vehicle unless the crank sensor-to-crankshaft relationship is disturbed. Removing a part for inspection and reinstalling the same part is considered a disturbance.

The crankshaft position system variation learn procedure must be performed when replacing the PCM in order to clear the DTC P1336. The crankshaft position system variation learn procedure is also required when the following service procedures have been performed whether or not DTC P1336 is set:

A fully warmed up engine is critical to learning the variation correctly. If a valid learn occurs, no other learns can be completed on that ignition cycle.

If the engine cuts out before the specified learn procedure engine speed or at normal fuel cut-off rpm, the PCM is not in the learn procedure mode. Review the Crankshaft Position System Variation Learning procedure and re-enable the learn procedure. Verify that the scan tool displays Test in Progress.

The numbers below refers to the step numbers on the Diagnostic Table.

2. The engine temperature is critical in order to correctly learn the Crankshaft Position System Variation. Failure to correctly warm the engine before performing this procedure will result in an inaccurate measurement of the Crankshaft Position System Learn Variation. The PCM learns this variation as the engine is decelerating and then allows the engine control to be returned to the operator. All accessories must be turned off. If the A/C is not disabled when the learn procedure is enabled, the PCM will disable the A/C. When the PCM is ready to allow the learn procedure to run, the scan tool will display Test in Progress.

3. If, after the specified number of attempts, the PCM cannot learn the Crankshaft Position System Variation, the variation is too large and no further attempts should be made until you correct the variation problem.