So after adding a can of R-134a at Advance today, I was on my way home looking forward to relaxing, and on comes the CEL. Back to advance, code pulled is P0420,
Bank 1: Catalyst Efficiency below threshold
So, is it common for the post-cat O2 sensor to go, or is it more likely the cat itself? Car is a 97 Cavalier with the 2.2L OHV, 132,400 miles. Other than that, the car is running absolutely beautifully. I haven't noticed any performance effects with the CEL, still runs just as smooth and isn't any slower than usual. So, O2 sensor, or cat. The NGK O2 sensor (post cat) is $87 plus tax, and the Cat itself is $180 plus tax and shipping. I'm not just going to replace one and have it be the other. Which is it most likely to be, and is there anyway to tell for sure?
neither will affect performance at all... only the pre-cat sensor really does anytihng...
The first o2 sensor should fluctuate rapidly... if it wasnt, you'd get a o2 sensor code.. (in theory.. lol)
The post-cat sensor reads for changes after the cat... and should be a fairly stable reading (meaning the cat is doing its thing).. if Its still fluctuating, you'll get a p0420...
Now if the post-cat sensor wasnt working... It probably wouldnt replicate the first sensors readings... that'd be a pretty funky malfunction.. lol..
I would say hook up a scanner and gather as much data as you can before anything else... what are your fuel trims like? etc.. That would be my first step...
i say at that mileage......02 sensor...i drove my cat til 185k
You need to compare pre cat to post cat O2 readings. My guess is that it is the cat though.
i got this p0420 after driving for a bit. i had just changed the upstream o2 sensor, so i cleared 3 times and never came back. but now after a year i just got the p0420 again. so now im stumped. like he said no performance change just the code. i have cleared it again and will see what happens.
~1996 Cavalier LS 2.4L (auto)
Letxen, please post what happens.
Everyone else..I had to change out my upstream o2 a while back because it was constantly reading slow. I changed it with the Bosch (yuck) but that was the only heated sensor I could find that fit the criteria. I spliced the power for that sensor off of the back o2....think water could have gotten in there and be altering the signal to through this code? Like letxen, my performance is not noticeably different.
Any help would be great.
Thanks,
Kevin
Kevin Kuntz wrote:Letxen, please post what happens.
Everyone else..I had to change out my upstream o2 a while back because it was constantly reading slow. I changed it with the Bosch (yuck) but that was the only heated sensor I could find that fit the criteria. I spliced the power for that sensor off of the back o2....think water could have gotten in there and be altering the signal to through this code? Like letxen, my performance is not noticeably different.
Any help would be great.
Thanks,
Kevin
you could have easily gotten once from your local GM dealer as you should have.
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I posted and looked and didn't find anything with concrete evidence that it worked. Do you have a part number of a heated replacement from the front o2? If so, please let me know.
Thanks for the response,
Kevin
Sure looks like it. I did a search with the 2.2L and it doesn't seem they sell/have that one on the website. Might be worth a call. 35 bucks for the one you specified seems reasonable.
does the rear o2 sensor need to be acdelco also?
~1996 Cavalier LS 2.4L (auto)
