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11-23-2022, 12:20 AM | #1 |
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Join Date: Jan 2001
Location: Orem, Utah
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P0420 and P0430 2002 Yukon
I have a 2002 Yukon XL with a 5.3 and automatic transmission. I couldn't get it to pass emissions after a tuneup (plugs, boots, two coils, cleaned MAF, replaced air filter, oil & filter change, fuel filter, Techron injector cleaner), so I replaced the catalytic converters and the rear O2 sensors. The O2 sensors are still reading low voltage (around 0.2v) but they're reading pretty steady. I'm not sure where to go next.
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11-23-2022, 01:35 PM | #2 |
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Re: P0420 and P0430 2002 Yukon
These are all very reasonable changes. They're what I would have done.
I have to ask a super dumb question, though (because everyone's level of experience with codes and code tools is different). You cleared the codes first, right? And then the codes keep popping up after being driven a while? One additional source for trouble code troubleshooting steps (at least for a couple of Hondas I used to work on) is going to the AllDataDIY.Com website. It's about $20 per vehicle per year. Not sure if GM does the step-by-step flowchart thing in their version of the shop manual, but the Honda one was pretty detailed. On one YouTube on a Ford (https://www.youtube.com/watch?v=-ZWKablBkwE&t=127s) suggested that cracked intake or coolant leak into the intake could cause those errors. Another YouTube (https://www.youtube.com/watch?v=zQ8BXAwK-QY) suggested it could be exhaust leaks skewing things. Good luck and please post back with your progress. This is interesting stuff.
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11-23-2022, 01:48 PM | #3 |
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Re: P0420 and P0430 2002 Yukon
I cleared the codes multiple times; I have a pretty decent scanner. Watching the live data, everything looked OK. Fuel trim was good, the rate of change on the upstream and downstream O2 sensors looked good, no misfires, and I couldn't figure out why the codes kept coming up. I finally decided to use some anti-foulers on the downstream O2 sensors. I was able to get it emissions tested today.
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11-26-2022, 08:13 AM | #4 |
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Location: Klein Texas
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Re: P0420 and P0430 2002 Yukon
Too much oxygen (low voltage) indicative of an exhaust leak. Broken exhaust manifold bolts?
Glad you got it to pass
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11-27-2022, 02:50 PM | #5 |
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Re: P0420 and P0430 2002 Yukon
whta brand of cats did you install? i made the mistake of ordering a $200 set of cat on my tahoe and got 8k miles out if them, ive had a dealer account have me install cheap cats that never worked out of the box.
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11-27-2022, 08:22 PM | #6 |
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Re: P0420 and P0430 2002 Yukon
They were cheaper cats. To be honest, as long as I get it to pass emissions that's all I care about.
BigDave, the only exhaust leak was the one where the two halves of the replacement cats meet where the stock crossover is located. The cuts for the flange are too deep. A little weld took care of it.
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I have sworn upon the altar of God, eternal hostility against every form of tyranny over the mind of man. - Thomas Jefferson |
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