The crankshaft position (CKP) system variation learn feature is used to calculate reference period errors caused by slight tolerance variations in the crankshaft, and the CKP sensor. The calculated error allows the engine control module (ECM) to accurately compensate for reference period variations. This enhances the ability of the ECM to detect misfire events over a wider range of engine speed and load.

The CKP system variation compensating values are stored in ECM memory after a learn procedure has been performed and the ignition switch is turned to the OFF position for at least 30 seconds. If the actual CKP variation is not within the CKP system variation compensating values stored in the ECM, DTC P0300 may set.

If the CKP system variation values are not stored in the ECM memory or a proper ECM power down does not occur after completing the CKP Learn Procedure, DTC P0315 sets.

The diagnostic runs continuously.

The ECM detects that the CKP system variation values are not stored in memory.

DTC P0315 is a Type A DTC.

DTC P0315 is a Type A DTC.

Scan Tool Reference

Important: The CKP System Variation Learn Procedure may have to be repeated up to 5 times before the procedure is successful.

1. Perform the Crankshaft Position System Variation Learn . The scan tool should display Learned this Ignition.
2. If the CKP System Variation Learn Procedure cannot be performed successfully, inspect for the following conditions:

•	Worn crankshaft main bearings

•	A damaged or misaligned reluctor wheel

•	Excessive crankshaft runout

•	A damaged crankshaft--Refer to Crankshaft and Bearing Cleaning and Inspection .

•	Interference in the signal circuit of the CKP sensor

•	The ignition switch is in the ON position until there is insufficient system voltage.

•	An ECM power disconnect with the ignition ON that may have erased the CKP system variation values and set DTC P0315

•	Debris between the CKP sensor and the reluctor wheel

⇒	If the control module is unable to complete the learn procedure, replace the control module.

Perform the Diagnostic Repair Verification prior to using this diagnostic procedure.

Control Module References for ECM replacement, setup, and programming