P1336

Diagnostic Chart:

Wiring Diagram:

CIRCUIT DESCRIPTION

The Crankshaft Position (CKP) sensor sends pulses to the VCM as the reluctor wheel teeth rotate past the CKP sensor. The VCM uses the CKP pulses to synchronize the ignition and fuel injector operation, and to time the interval between each CKP pulse. The VCM determines when an excessive change in crankshaft speed occurs by comparing each new time interval with the previous interval. A misfire causes an unexpected change in the crankshaft speed. A certain amount of acceleration/deceleration is expected between each firing stroke, but if the crankshaft speed changes more than an expected amount, the VCM interprets this as a misfire. The interval between CKP sensor pulses is extremely small. 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 detect misfire calculations. Only a scan tool can command the VCM to perform the Crankshaft Position System Variation Learning Procedure again.

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

^ The ignition switch is in the ON position ur1til the battery is drained

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 SETTING THE DTC

^ Engine running

^ Manufacturer's Enable Counter must be zero

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 the MIL OFF after 3 consecutive drive trips when the test has Run and Passed and not Failed.

^ 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 exceeds 70°C (160°F) during the same ignition cycle).

^ Use the scan tool Clear Information function.

^ Disconnect the VCM battery feed for 30 seconds.

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 VCM will not allow the scan tool to enable the learn procedure, if the VCM receives an incorrect crankshaft to camshaft ratio.

Engine diagnostic misfire is not operable when the engine is above 1000 RPM and DTC P1336 is set.

When the learn procedure is in progress and the engine speed is at 4000 RPM, a decrease in engine speed will occur. During the engine coastdown, 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 misfire.

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.