WARNING: This page is about a different car, the 2003 Oldsmobile Bravada, 2003 GMC Envoy XL, 2003 GMC Envoy, and 2003 Chevrolet TrailBlazer. However, it is still accessible from the selected car via links, so may be relevant.
The number below refers to the step number on the diagnostic table.
3. If any of the listed DTCs are set, the PCM will not receive and learn a valid password.