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P0420 please help!

Tiny
DOCFIXIT
  • MECHANIC
  • 18,828 POSTS
Does not sound like they did. Cats don't go bad that often for your mileage and they go when thereis an engine miss, injector leaking. You have an O2 in front and one after Cat the PCM compares the two readings. If it does not see the right results it set a code. An exhaust leak or O2 will cause code. A scan of PCM by a qualified Tech would show fault.
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Wednesday, May 20th, 2020 AT 1:34 PM (Merged)
Tiny
BKSFLYESTPAPI333
  • MEMBER
  • 25 POSTS
Well I will admit that the cat might have been bad because I had a misfire on cylinder three for a while which eventually caused a multiple misfire on two cylinders. The misfire was going on for about a year. I know it's a long time but these mechanics can be so full of themselves around here where I live so I dont trust them too much. But even if the cat was bad, there is obviously something else wrong for the code to continue to pop up. By "scan of PCM", you mean a diagnostic test?
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Wednesday, May 20th, 2020 AT 1:34 PM (Merged)
Tiny
DOCFIXIT
  • MECHANIC
  • 18,828 POSTS
Yes they will read the outputs of the O2 s and other sensors to determine why code is setting. Ask around try fine an A.S.E. Certified shop but keep in mind a non GM cat will cause the code
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Wednesday, May 20th, 2020 AT 1:34 PM (Merged)
Tiny
BKSFLYESTPAPI333
  • MEMBER
  • 25 POSTS
Ok so the code might just be because of the non GM cat? Does the non GM cat work just as good as a GM cat?
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Wednesday, May 20th, 2020 AT 1:34 PM (Merged)

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