Diagnostic Aids

WARNING: This page is about a different car, the 2003 GMC Sierra, 2003 GMC Cab & Chassis Sierra, 2003 Chevrolet Silverado, and 2003 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

NOTE: 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.

NOTE: Poor engine performance can sometimes be diagnosed as a transmission driveability condition. To avoid mis-diagnosis of the automatic transmission, always perform powertrain diagnostic system check. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE.

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:
1. TCM power is interrupted.
2. The ignition is turned off.
3. The battery voltage level is very low.
4. A poor connection at the Diagnostic Link Connector (DLC).