GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The PCM has the ability to dtermine the amount of offset needed to bring the engine to top dead center. This is used by the PCM to determine proper injection time.

Conditions for Running the DTC

The engine is operating.

Conditions for Setting the DTC

The TDC offset is greater than 2.46 degrees

or

The TDC Offset is less than -2.46 degrees.

Action Taken When the DTC Sets

    • The PCM illuminates the malfunction indicator lamp (MIL) on the second consecutive drive trip that the diagnostic runs and fails.
    • The PCM records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the Failure Records will store this information. If the diagnostic reports a failure on the second consecutive drive trip, the Freeze Frame records the operating conditions at the time of failure and updates the Failure Records.

Conditions for Clearing the MIL/DTC

    • The PCM will turn the MIL off after three consecutive trips without a fault condition.
    • A History DTC clears after forty consecutive warm-up cycles, if this or any other emission related diagnostic does not report any failures.
    • Use of a scan tool

Diagnostic Aids

The PCM will only run the diagnostic test when a TDC Offset adjustment procedure has been activated. It is highly unlikely that the vehicle will be brought in with this DTC set. Refer to