CKP System Variation Learn Procedure

NOTE: A Crankshaft Position (CKP) system variation learn procedure must be performed any time a change is made to the crankshaft sensor-to-crankshaft relationship. Changing the crank sensor to crankshaft relationship will not allow the PCM to detect misfire at all speeds and loads accurately, resulting in a possible false misfire DTC being set.

Removing a part for inspection and then reinstalling the same part is considered a disturbance. A false DTC P0300 could be set if this procedure is not performed.

The learn procedure is required after the following service procedures have been performed, regardless of whether or not DTC P1336 is set: A PCM replacement, an engine replacement, crankshaft replacement, CKP sensor replacement, or any engine repair which disturbs the crankshaft/harmonic balancer relationship to the crankshaft position sensor.

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 learn procedure and re-enable the learn procedure. Verify that the scan tool displays Test In Progress.

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

NOTE: The battery must be fully charged and in good condition. Verify that the scan tool connection at the Data Link Connector (DLC) is clean and tight before starting the crankshaft position system variation learn procedure.

Close hood.
Block drive wheels and set vehicle parking brake.
Place vehicle in Park or Neutral.
Turn all accessories OFF.
Connect scan tool.
Start and operate engine to normal operating temperature of 185°F (85°C).
With engine still running, use scan tool in order to enable the Crankshaft Position (CKP) system variation learn procedure.
Depress and hold brake pedal firmly and raise engine speed to 3920 RPM, RELEASING the throttle as soon as engine cuts out.
Verify with scan tool that crankshaft variation has been learned.

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 variation will not learn, perform this test procedure up to 10 times.

Excessive crankshaft variation can be caused by the following factors. See EXCESSIVE CRANKSHAFT VARIATION SYMPTOMS table.

EXCESSIVE CRANKSHAFT VARIATION SYMPTOMS

Scan Tool Display	Possible Cause
Factors Out Of Range	Reluctor Wheel - Machining Quality, Run-Out or Incorrect Air Gap.
Opposing Factors Out Of Range	Disturbance - Noise on CKP Sensor Circuit. Re-attempt Learn Procedure.
Sum Out Of Range	Engine Too Cold. Re-attempt Learn Procedure.
Crank Pulse Count Error	Crank Or Cam Sensor DTC Is Set. Repair Affected DTC First.