Conditions for Updating the I/M System Status

WARNING: This page is about a different car, the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, and 2004 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

Each system monitor requires at least one, and sometimes several, diagnostic tests. The results of these tests are reported by a DTC. A system monitor completes when either all DTCs comprising the monitor have run and passed, or any DTC comprising the monitor has illuminated the malfunction indicator lamp (MIL). Once the monitor completes, the I/M System Status display will indicate YES in the Completed column. For example, when the Misfire Monitoring System Status display indicates YES, all of the misfire components have been diagnosed. The I/M System Status will indicate NO in the Completed column when any of the required DTCs for that system have not run. The following is a list of conditions that would set the I/M System Status indicators to NO:

The vehicle is new from the factory and has not yet been driven through the necessary drive conditions to complete the system monitor.
The battery has been disconnected or discharged below operating voltage.
The control module power or ground has been interrupted.
The control module has been reprogrammed.
The control module DTCs have been cleared as part of a service procedure.