Diagnostic Question

  • 6 CYL
  • 4WD
  • 31,700 MILES
I recently had my battery changed. I then failed my state's emissions test because the oxygen sensor and catalytic converter were "not ready." I drove the car for 6 weeks and then was re-tested. I failed again for the same reason. My mechanic says I need to drive around even more! Is this good advice? Or is there something wrong with my oxygen sensor and/or catalytic converter?
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Monday, January 17th, 2011 AT 2:33 PM

1 Reply

This must be "wont pass emissions" day here at 2CarPros! The advice is good, but it also might need some clarification, the emissions testing process requires that the monitors to run to completion, this is done by following the set standards of the OBDII according to the car maker, they can vary slightly from car to car. In a nut shell, the car should be started from cold, and I mean sitting overnight, then allowed to idle for at least one minute, then driven for perhaps 20 minutes in a continous fashion. Do not exceed 3000 rpm. The fuel tank should be between one quarter and three quarters full. The drive cycle should be on the freeway and on surface streets. I would take a car that I had just reset the monitors on and let it sit to get cold, then start it and wait until the temp gauge starts to move off the cold peg, then without ever exceeding 3k rpms, drive the car to a 10-15 mile length of freeway and cruise normally, once again without exceeding 3k rpms, getting off the freeway and run the same road to return to the shop. This always ran the monitors to completion. And then I could smog the car. The monitors that you have stated that have not completed are the last ones to complete, driving your car in the suggested manner should allow them to be complete and then the emission testing can be done.
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Monday, January 17th, 2011 AT 4:16 PM

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