Test Status

There are many tests waiting to be performed once the vehicle is started. It is the Task Manager's job to ensure that these tests are performed under the appropriate conditions.

An additional job of the Task Manager is to prevent false Diagnostic Trouble Codes (DTC's) from being stored. The Task Manager accomplishes this by not running certain tests when it recognizes that faults already in the system or tests currently being run could cause the next test to fail erroneously. For example:

^ The test for the catalyst monitor does not run if the Malfunction Indicator Lamp (MIL) is illuminated due to an oxygen sensor fault. The oxygen sensor is a key component in the catalyst monitor test. If the sensor is not functioning properly, there is no reason to run the catalyst monitor - it may not pass. This test will not be run, pending repair of the sensor fault.

^ The Task Manager does not run the test to monitor catalyst operation if the EGR monitor test is being run. The EGR monitor is an "intrusive" test, and will cause the catalyst monitor to produce data not representative of normal operating conditions. This represents a conflict of test data. The Task Manager will wait until the EGR monitor is finished before running the catalyst monitor.

^ Finally, the results from the catalyst monitor are always held until the oxygen sensor test has been completed successfully. The results from the test are suspended until the required prerequisite test has been completed.

By reviewing these guidelines, the Task Manager avoids storing DTCs that are the result of failure of other components in the system. The Task Manager allows you to use the diagnostic scan tool more confidently in diagnosing and repairing a fault.