Conditions for Updating the I/M System Status

Each system monitor requires at least one, and sometimes several, diagnostic tests. The result of each test is reported by a diagnostic trouble code (DTC). A system monitor is complete when either all of the DTCs composing the monitor have Run and Passed, or when any one of the DTCs comprising the monitor has illuminated the malfunction indicator lamp (MIL). Once the system monitor is complete, the inspection/maintenance system status display will indicate YES in the Completed column.

For example, when the HO2S Heater Monitor indicates YES, either all of the oxygen sensor heater tests have passed or one of the tests has illuminated the MIL. If the vehicle has two heated oxygen sensors, either both heater circuit tests have passed or one of the heater circuit tests has illuminated the MIL. The inspection/maintenance system status will indicate NO under the completed column when any of the required tests for that system have not run. The following is a list of conditions that may set the inspection/maintenance system status indicator to NO:

• The vehicle is new from the factory and has not yet been driven through the necessary drive conditions to complete the tests.
• The battery has been disconnected or discharged below operating voltage.
• The engine control module (ECM) power or ground has been interrupted.
• The ECM has been reprogrammed.
• The ECM DTCs have been cleared.