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 when any one of the DTCs comprising the monitor have illuminated the Malfunction Indicator Light (MIL). Once all of the tests have been completed, the I/M system status display will indicate YES in the completed column. For example, when the HO2S heater test indicates YES, all oxygen sensor heaters and 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 will set the I/M system status indicator to NO:

• Vehicle is new from the factory and has not yet been driven through the necessary drive conditions in order to complete the tests.
• Battery has been disconnected or discharged to less than operating voltage.
• Control module power or ground has been interrupted.
• Control module has been reprogrammed.
• Control module DTCs have been cleared as part of a service procedure.