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Forum > Failed Smog Test > Question

Mitsubishi Galant check engine light is on and the CAT is bad.

I tried to get it smogged and they said the CAT was bad and my check engine light is on. I noticed the problem when I was trying to get home and the gas ran out. Every since then the trouble code has been on. The car runs great and I don't notice any performance difference with my car. My question is if i clean the oxygen sensors will that fix the problem, or do I need to replace the CAT?
Answer:

Cleaning an oxygen sensor is not recommend and will not improve performance. Oxygen sensors need to be replaced typically every 30-50 thousand miles. We also do not recommend jumping the gun and replacing the CAT without a thorough diagnosis. First thing that should be done is the check engine light needs to be diagnosed. Once the trouble codes are pulled from the engine computer a smog check technician and inspect the component or system causing the light to illuminate. If in fact the problem is with an oxygen sensor it will need to be replaced. The CAT is always the last component to suspect and/or replace. Mike - SmogTips Support posted by SmogTips Support

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