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Q: What's at fault, is it my computer module, a bad CAT, or a sensor?

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So my pickup has a single straight pipe I keep getting a check engine light that turns on and off when it wants to one week it says bad O2 sensor the next it's something with my CATs (I can read these codes with my programmer) I have a video of it starting on a 40 degree morning and it sounds horrible. I've had people tell me it's my computer module? When it gets cold like in the teens it barely starts.

My car has 119000 miles.
My car has an automatic transmission.

A: Hi there. The codes would be helpful and do...

Hi there. The codes would be helpful and don't clear them. A sticking O2 sensor can cause drivability issues and set the Check Engine Light. If there is a catalytic converter code, I would focus first on the O2 sensor code and get that corrected and monitor the catalytic converter code to see if it returns. If it returns, then proceed with further diagnosis of the converter code. The ECM being faulty is a possible cause, but without proper inspection I would not recommend replacement.

Starting with diagnosing and correcting the codes is the best route to see if what is setting the codes is also causing the cold start issues. I strongly suggest acquiring a qualified technician to perform an inspection to avoid replacing unnecessary parts. YourMechanic has several available technicians that can assist you with a Check Engine Light inspection at your own location.

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