The last step is to verify the repair. Again, who is going to test your repair better than the PCM? This can be done in a few ways. You can research the drive-cycle requirements for the monitor associated with the DTC you repaired and drive the car accordingly.

To do this, clear the codes using Mode $04 on your scan tool. This will reset all monitors as well. Drive the car and recheck the monitor status. If all monitors have completed, you can check for pending codes to see if the fault has returned or if there is one that went untested because its monitor was disabled by the first fault. Remember the "not completed" oxygen sensor and catalyst monitors in this example? It is also a good idea to check the Mode $06 test results for the monitors to make sure that all tests passed. You don't have to be a Mode $06 expert to do this. Just look for test results that look close to their limits or an individual test that is listed as "failed." If you find this, you will have to do some more research to identify exactly what the test is for and what monitor it is a part of.

You can also emulate the PCM tests yourself by learning what tests are involved and how the PCM conducts them. This is also going to take some effort on your part, but as you continue to develop your skills at thinking like the PCM, you'll find the effort gets easier and easier, your comebacks become fewer and fewer, and your customers get happier and happier.

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