Conditions for Updating I/M System Status

Each system requires at least one, and sometimes several, diagnostic tests. The results of these tests are reported by a Diagnostic Trouble Code (DTC). A system monitor is complete when either all of the DTCs comprising the monitor have Run and Passed, or any one of the DTCs comprising the monitor have illuminated the Malfunction Indicator Lamp (MIL). Once all of the tests are complete, the I/M System Status display will indicate YES in the Completed column. For example, when the Heated Oxygen Sensor (HO2S) Heater Test indicates YES, all of the oxygen sensor heaters have been diagnosed. If the vehicle has four heated oxygen sensors, all four heater circuits have been diagnosed. The I/M 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 would set the I/M 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 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.