Skip the auto shop - Our mechanics make house calls

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

asked by on

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.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Save up to 30%

Get a quote

What others are asking

Q: Should I replace or clean the catalytic converter?

Hey there. The Check Engine Light can set if the catalyst efficiency is below threshold. There will be no visible symptoms at all, or change in engine performance, because the recorded "low efficiency" can simply mean that more pollutants are...

Q: Sometimes my car has a rough idle and even stalls - 2004 Chevrolet Tahoe

Hello. From my experience with this engine, the issue is usually due to the fact that the throttle body plate is worn out in the bore, or, more commonly, it is caused by an issue with the intake manifold gasket...

Q: Car starts and then dies, think my ECM is bad.

Hi there. If the security is on and you are not able to shut it off, then there could be a faulty key transponder, security control module, faulty key fob, or the key cylinder has failed. The ECM (computer to...

Related articles

How Do Power Car Windows Increase Passenger Safety?
Power windows are responsible for approximately 2,000 emergency room visits every year. When a power window closes, it exerts enough force to bruise or break bones, crush fingers, or restrict an airway. Though...
What Causes Hoses to Leak?
While the largest part of your engine is mechanical, hydraulics plays a significant role. You’ll find fluids at work in a number of different areas. Your car's fluids include: Engine oil Transmission...
How to Avoid Back Pain in a Car
If you have back problems, sitting in a car for an extended period of time can be excruciating. Even without back problems, you could experience discomfort and soreness from...