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 are 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.
The PCM power or ground has been interrupted.
The PCM has been reprogrammed.
PCM DTCs have been cleared as part of a service procedure.

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.

• Brakes feel soft, pull hard to one side, or make grinding noises.

• The engine overheats, stalls repeatedly, or misfires under load.

• You are missing required tools, torque specs, or safe lifting equipment.

• You are not confident in the next step or safety outcome.

Safety Warning

Conditions For Updating I/M System Status

Use the Manual With the Right Hardware

When to See a Mechanic