Diagnostic Aids

HO2S heater tests will normally run within 2 minutes allotted in procedure. If there is impending failure, system may require more time to run diagnostic than was allotted in set procedure. If test does not update within 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 loss of enabling conditions. Extremely high ambient temperatures may prevent HO2S heater test from initiating.

First failure of a type "B" DTC does not constitute a final determination of pass or fail, and will not update I/M system status to YES. A second trip is required, and all conditions to run must be met in order for test to run again. These conditions may include a partial or complete engine cool down. I/M system status will update only when DTC fails second time, or if all tests pass.

If a diagnostic test is difficult to run, observe I/M system status display while maintaining necessary enable conditions until system status updates to YES.