Reader Question: Austin, I failed the emission test for the yearly inspection in NC and had the catalytic converter changed and then went to a station to have the check engine light programmed so that it was turned off. All appeared to be ok and I drove it twice without the check engine light coming back on but today as I was driving home from work the light came on again.
I am inquiring as to what is causing this problem or does the light need to be reprogrammed? In order to get my car inspected I was told I had to cold drive it at 55mph for 5 minutes which is almost impossible to do and I am wondering if that has anything to do with the light coming backon. Any assistance provided will be greatly appreciated. Thank you. Patrick
Thanks for your email Patrick
I think you probably still have problem, and that is why your check engine light is coming on. A bad, or non working catalytic converter can cause you to fail the emission test, but there are also many sensors on the engine that can fail, turn on the check engine light AND cause you to fail the emission test.
Was your old converter REALLY bad or did you replace it because you thought that was the cause of your emission failure?
I would start over from square one and have the check engine light diagnosed. The mechanic can read the onboard computer codes and see what code is returning and causing the check engine light to come on.
The engine light will only come on when it catches a problem, so you might have a sensor that is failing intermittently and when it does fail the check engine light comes on.
Resetting the light will probably only turn it off until the problem shows up again, then it will come back on. In Texas….as long as the check engine light is NOT on when the inspector runs the emission test, you can still take the test. If the light is on, they are not supposed to perform the test at all.
It is recommended that the vehicle be driven a few minutes at highways speeds prior to taking the emission test to make sure the catalytic converter is nice and hot and has removed any carbon debris that might be in the exhaust system from an initial start up. Bringing the engine up to normal operation temperature (210 Degree F) will help ensure the engine is not “running rich” and give you a better chance of passing the test.
Here is more info on check engine lights
Keep me posted,
Austin C. Davis