P1336
DTC P1336 CKP System Variation Not Learned
Circuit Description
The Crankshaft Position (CKP) Sensor is mounted in the front of the engine behind the harmonic balancer. The CKP sensor works in conjunction with a 3X (4x on V8 applications) reluctor wheel mounted on the front of the crankshaft. The CKP sensor has a B+ power supply, a ground, and a signal circuit.
As the crankshaft rotates, the reluctor wheel teeth interrupt a magnetic field produced by a magnet located in the sensor. The sensor's internal circuitry detects this field and produces a frequency which the VCM monitors on the signal circuit. The VCM uses this signal to accurately measure crankshaft velocity which is important to ignition control spark timing, fuel injector timing and for misfire detection.
The VCM can detect small variations in the CKP sensor and reluctor wheel. These parts tolerances must be learned by the VCM before an accurate CKP signal can be determined. At high engine speeds, slight variations in the following components make misfire detection difficult:
- Crankshaft
- Reluctor wheel
- CKP sensor
The VCM learns variations during the Crankshaft Position System Variation Learning Procedure. The VCM compensates for these variations when performing misfire calculations. Only a scan tool can command the VCM to perform the Crankshaft Position System Variation Learning Procedure. Perform the learning procedure after the following actions:
- A VCM replacement
- Any operation or repair involving the crankshaft, the CKP sensor, or the CKP sensor to reluctor wheel gap relationship
- An engine replacement
IMPORTANT: A VCM power disconnect with the ignition ON may erase the stored pulse value and set the DTC P1336.
Disconnecting the VCM will not erase the learned Crankshaft Position System Variation as long as the ignition switch is in the OFF position.
IMPORTANT: Reprogramming the VCM does not require running the Crankshaft Position System Variation Learn Procedure unless the VCM is new or from another vehicle.
If the Crankshaft Position System Variation is not within an acceptable range, or can not be learned, DTC P1336 sets.
Conditions for Running the DTC
- The engine is running
- No active CMP sensor DTCs
- No active CKP sensor DTCs
Conditions for Setting the DTC
The VCM has not learned the crankshaft position system variation.
Action Taken When the DTC Sets
The VCM will illuminate the Malfunction Indicator Lamp (MIL) on the first drive trip that the diagnostic runs and fails.
Conditions for Clearing the MIL/DTC
- The VCM turns OFF the MIL after 3 consecutive drive trips when the test has Run and Passed.
- A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles (coolant temperature has risen 22 °C (40 °F) from the startup coolant temperature and the engine coolant temperature is more than 70 °C (158 °F) during the same ignition cycle).
- Use the scan tool Clear Information function.
Diagnostic Aids
Check for the following conditions if the Crankshaft Position System Variation Learn Procedure cannot be learned.
- A chipped or damaged reluctor wheel
- Incorrect alignment of the CKP sensor to the reluctor wheel
- Excessive crankshaft run-out
- Interference in the signal circuit to the CKP sensor
- Incorrect ratio of crankshaft to camshaft pulses
IMPORTANT: The VCM does not allow the scan tool to enable the learn procedure when an incorrect crankshaft to camshaft ratio is received.
The engine misfire diagnostic is disabled when the engine speed is above 1,000 RPM and this DTC is active.
When the learn procedure is in progress and the engine speed is at 4,000 RPM, a decrease in engine speed will occur. During the engine coast down, the VCM monitors the CKP sensor signal and stores the pattern. This pattern is used to determine if the crankshaft speed variations are due to an engine misfire.
An intermittent may be caused by any of the following conditions:
- A poor connection
- Rubbed through wire insulation
- A broken wire inside the insulation
Thoroughly check any circuitry that is suspected of causing the intermittent complaint. Refer to Intermittents and Poor Connections Diagnosis.
If a repair is necessary, then refer to Wiring Repairs or Connector Repairs.
Steps 1 - 3:
Steps 4 - 8:
Test Description
The number(s) below refer to the step number(s) on the diagnostic table.
2. The VCM enables the learn process after 65 °C (150 °F) is reached. Engine deceleration occurs when the learn procedure is in progress. The VCM monitors and records the CKP sensor signal during engine coast down conditions.
3. TEST IN PROGRESS on the scan tool indicates the VCM is performing the learn procedure. If the VCM receives an incorrect crankshaft to camshaft pulse ratio, an incorrect transmission range signal input, corrupted communication, or no change in the brake switch input, the learn procedure will not be allowed.
4. If a repair is necessary due to a condition which prevented the learn procedure from enabling, the Crankshaft Position System Variation Learning Procedure must be performed
5. The ignition must be in the OFF position for at least 10 seconds after the learn procedure is complete and the engine RPM has returned to idle. The VCM saves the signal data after these conditions are met.