Check Engine Indicator Illuminated, DTC PO446 (Diagnose and Repair/Replace PCM)

Some customers may comment that the Check Engine indicator is/was illuminated.

Under certain types of driving conditions, there may be a false setting of DTC P0446.

1. Perform the Powertrain On-Board Diagnostic (OBD) check as outlined in Service Information.
2. Is DTC P0446 the only DTC recorded? If YES, go to Step 4. If NO, continue with the next Step.
3. Perform all Service Manual diagnostics/repairs for any other codes stored.
4. Inspect the Evaporative Emission Vent System (EVAP) using the Service Manual. Pay particular attention to the EVAP switch solenoid wiring harness connections for conditions which may cause an intermittent condition.
5. If normal diagnostic procedures do not result in a cause identification, replace the PCM. This PCM is not reprogrammable and will require replacement with a PCM which has upgraded software. For correct part number identification see the table in Parts Information.

For PCM replacement procedures, follow the procedures as outlined in the Service Manual.

Inspect the underhood emission label for the emission certification area (California/Federal) for use in the following table to determine the correct part number.

Parts are expected to be available from GMSPO, 11/30/00.

For vehicles repaired under warranty, use:

Important: This repair is covered under the Federal Emission Warranty for 1999 vehicles - 8 years or 80,000 miles.