P1336

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 sensors internal circuitry detects this field and produces a frequency which the Powertrain Control Module (PCM) monitors on the signal circuit. The control module uses this signal in order to accurately measure crankshaft velocity, which is important to ignition control spark timing, fuel injector timing, and for misfire detection.

The control module can detect small variations in the CKP sensor and reluctor wheel. These pant tolerances must be learned by the control module 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 control module learns variations during the Crankshaft Position System Variation Learning Procedure, and compensates for these variations when performing misfire calculations. Only a scan tool can command the control module to perform the Crankshaft Position System Variation Learning Procedure.

Perform the learning procedure after the following actions:
^ A control module 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 control module power disconnect with the ignition ON may erase the stored pulse value and set the DTC P1336.

Disconnecting the control module will not erase the learned crankshaft position system variation as long as the ignition switch is in the OFF position.

IMPORTANT: Reprogramming the control module does not require running the Crankshaft Position System Variation Learn Procedure unless the module is new or from another vehicle.

If the crankshaft position system variation is not within an acceptable range, or cannot be learned, DTC P1336 sets.

CONDITIONS FOR RUNNING THE DTC
The engine is running.

CONDITIONS FOR SETTING THE DTC
The PCM has not 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.
^ Use a scan tool in order to clear the MIL and the DTC.

DIAGNOSTIC AIDS
If the Crankshaft Position System Variation Learn Procedure cannot be learned, check for the following conditions:
^ 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 PCM will not allow the scan tool to enable the learn procedure if the PCM receives an incorrect crankshaft to camshaft ratio.

Engine diagnostic misfire is not operable when the engine is more than 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 PCM monitors the CKP sensor signal and stores the pattern. This pattern is used to determine if the crankshaft speed variations are due to an 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 inspect any circuitry that is suspected of causing the intermittent complaint. Refer to Testing for Intermittent and Poor Connections in Diagrams.

If a repair is necessary, refer to Wiring Repairs or Connector Repairs in Diagrams.

TEST DESCRIPTION

Steps 1-9:

The numbers below refer to the step numbers on the diagnostic table.
2. The PCM enables the learn process after 65°C (150°F) is reached. Engine deceleration occurs when the learn procedure is in progress. The PCM monitors and records the CKP sensor signal during engine coast down conditions.
3. TEST IN PROGRESS on the scan tool indicates the PCM is performing the learn procedure. If the PCM 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 Learn 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 PCM saves the signal data after these conditions are met.