Circuit Description
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 crankshaft position sensors. The calculated error allows the powertrain control module (PCM) to accurately compensate for reference period variations. This enhances the ability of the PCM to detect misfire events over a wider range of engine speed and load.
The PCM stores the crankshaft position system variation values after a learn procedure has been performed. Diagnostic trouble code (DTC) 1336 set indicates that the crankshaft position system variation values have not been stored in the PCM and the crankshaft position system variation learn procedure must be performed. The learn procedure is required after the following service procedures have been performed, regardless of whether or not DTC P1336 is set:
| • | PCM replacement |
| • | PCM reprogramming |
| • | Engine replacement |
| • | Crankshaft replacement |
| • | Crankshaft position sensor replacement |
| • | Any engine repair that disturbs the crankshaft to crankshaft position sensor relationship |
Conditions for Running the DTC
| • | DTCs P0335, P0336, P0340, P0341, P0385, P0386, or P1372 are not set. |
| • | The engine coolant temperature is more than 70°C (158°F). |
Conditions for Setting the DTC
The crankshaft position system variation values are not stored in the PCM memory.
Action Taken When the DTC Sets
| • | The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails. |
| • | The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records. |
Conditions for Clearing the MIL/DTC
| • | The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail. |
| • | A current DTC, Last Test Failed, clears when the diagnostic runs and passes. |
| • | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic. |
| • | Clear the MIL and the DTC with a scan tool. |
Diagnostic Aids
The crankshaft position system variation compensating values are stored in PCM memory after a learn procedure has been performed. If the actual crankshaft position variation is not within the crankshaft position system variation compensating values stored in the PCM, DTC P0300 may set. Refer to Diagnostic Aids for DTC P0300.
Step | Action | Yes | No |
|---|---|---|---|
1 | Did you perform the Diagnostic System Check-Engine Controls? | Go to Step 2 | |
2 | Perform the crankshaft position system variation learn procedure. Refer to Crankshaft Position System Variation Learn . Is the action complete? | Go to Step 3 | -- |
3 | With a scan tool observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | System OK |
