Diagnostic Aids

The HO2S heater tests will normally run within the 2 minutes allotted in the procedure. If there is an indeterminate condition, test may take up to 8 minutes on some vehicles before a decision of pass or fail is made. If test does not update within the allotted period of time, continue operation within enable conditions until test updates to YES. If test does not update to YES, it may have failed or aborted due to the loss of enabling conditions. Extremely high ambient temperatures may prevent HO2S heater test from initiating.

The I/M System Status does not indicate whether test has passed or failed, only that a decision was made. When all of the diagnostics for a specific system have run and passed, I/M System Status will update to YES. If a test for a specific system has failed, I/M System Status will update to YES, indicating a determination was made, even if all of the required tests have not run. When a failure occurs, the emission related DTC portion of the I/M System Status display will indicate that MIL is requested. The I/M System Status also registers the DTCs.