Diagnostic Aids: Notes

WARNING: This page is about a different car, the 2003 Pontiac Aztek and 2003 Buick Rendezvous. However, it is still accessible from the selected car via links, so may be relevant.

Important:

Do not clear the DTC unless directed by a diagnostic procedure. Clearing the DTCs will erase all Freeze Frame and Failure Records stored in PCM memory.
Poor engine performance can sometimes be diagnosed as a rear axle driveability condition. In order to avoid mis-diagnosis of the rear axle, always perform DIAGNOSTIC STARTING POINT -- ENGINE CONTROLS .
Use a scan tool that is known to function correctly. If necessary, test the scan tool on another vehicle.
Ensure the scan tool contains the most current file available.
The scan tool will display a loss of communication error message under the following conditions:

The PCM power is interrupted.
The ignition switch is turned OFF.
The battery voltage level is very low.
A poor connection at the diagnostic link connector (DLC).