So I changed the o2 sensor behind cat, drove it a solid 200+miles and today it came back on. Any suggestions?

 

Factory down pipe and cat?

IF so the cat might be burnt out and not functioning properly.

 

What is the actual code number? There might be some more data looking up the specific code. Also, what brand O2 did you use? Bosch O2's have had a history not working the greatest with the 3800 (AC Delco and Delphi are the best ones).

 

Its not a Bosch, but not a Delco or Delphi. Maybe ill try a Delco if this trips the CEL again. Thanks

 

Our Montes like nothing but AC Delco replacement parts and operate at peak performance.

 

Yes, I'm seeing a pattern with you Monte guys lol, I'll move to a Delco thanks!

 

i have exact same issue, no matter what i do, cat or sensors the light comes back on in 2 or 3 days.

 

no wiring issues, no shorts, no other issues with the car, just the friggin cel i cant get to stay out. im looking into selling the car cause of it.

 

Did you run the car through a drive cycle after replacement? If certain conditions are not met the test cycle for the O2 sensors will not run and the PCM will set the code.

GM General Motors OBD Driving Cycle

As Jason mentioned, a code would be helpful to narrow down possibilities if the drive cycle doesn't reset the CEL.

 

its the P0141 - i replaced the o2 last weekend, drove both city and highway, about 200+miles, and it popped on early in the morning about 1 mile away... Its not a Delco o2 sensor, and I'm hearing those are the only ones that work with these cars.