For 1990-2009 cars

### Circuit Description

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 DTC P1336 is set:

• | PCM replacement

• | Engine replacement

• | Crankshaft replacement

• | Crankshaft balancer replacement

• | Crankshaft position sensor replacement

• | Any engine repairs which disturbs the crankshaft/harmonic balancer to the crankshaft position sensor relationship

The PCM measures the variations, 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.

### Conditions for Setting the DTC

• | There are no crank or cam sensor DTCs.

• | The PCM has not successfully learned the Crankshaft Position System Variation.

### 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

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, then 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 PCM replacement

• | An engine replacement

• | A crankshaft replacement

• | A crankshaft balancer replacement

• | A crankshaft position (CKP) sensor replacement

• | Any engine repair which disturbs the crankshaft/harmonic balancer-to-crankshaft position sensor relationship

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.

#### Excessive Crankshaft Variation Symptom

Scan Tool Display | Possible Causes
--- | ---
Factors out of range | The reluctor wheel-machining quality, a run out, or an incorrect air gap.
Opposing factors out of range | Disturbance-Noise on the crank sensor circuit. Reattempt the Learn Procedure.
Sum out of range | The engine is too cold. Reattempt the Learn Procedure.
Crank pulse count error. | Crank or Cam sensor DTCs is set. Repair the affected DTC first

### Test Description

The numbers below refer to the step numbers on the diagnostic table.

1. 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.

2. 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.

#### DTC P1336 - Crankshaft Position System Angle Variation Not Learned

Step | Action | Yes | No
--- | --- | --- | ---
1 | Did you perform the Diagnostic System Check-Engine Controls? | Go to Step 2 | Go to Diagnostic System Check - Engine Controls
2 | Perform the Crankshaft Position System Variation Learn procedure. Refer to Crankshaft Position System Variation Learn . Does the scan tool indicate that the crankshaft position system variation has been learned? | Go to Step 4 | Go to Step 3
3 |

1. Turn OFF the ignition.
2. Inspect the crank sensor to crankshaft relationship. Refer to the Excessive Crankshaft Variation Symptom Table.
3. If a problem is found, repair as necessary.

Did you find and correct the condition?

Go to Step 4

Go to Diagnostic Aids

4 |

1. Use the scan tool in order to clear the DTCs.
2. Turn OFF the ignition for 30 seconds.
3. Start the engine.
4. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC run and pass?

Go to Step 5

Go to Step 2

5 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | Go to Diagnostic Trouble Code (DTC) List | System OK