GM Service Manual Online
For 1990-2009 cars only

Emissions Related DTCs

Action Taken When the DTC Sets - Type A

    • 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.

Action Taken When the DTC Sets - Type B

    • The control module illuminates the MIL on the second or third consecutive ignition cycle that the diagnostic runs and fails.
    • When the diagnostic reports a failure on the second or third consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame/Failure Records.

Conditions for Clearing the MIL/DTC - Type A or Type B

    • The control module turns OFF the MIL after 3 or 4 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.

Non-Emissions Related DTCs

Action Taken When the DTC Sets - Type C

    • The control module stores the DTC information into memory when the diagnostic runs and fails.
    • The MIL will not illuminate.
    • The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.
    • The driver information center, if equipped, may display a message.

Conditions for Clearing the DTC - Type C

    • A last test failed, or current DTC, 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 non-emission related diagnostic.
    • Use a scan tool in order to clear the DTC.