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Codes P0138 and P2271 on a 2009 Avalanche 5.3

hwkmn1

New Member
Joined
Oct 26, 2020
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3
P0138 = H02S Circuit High Voltage Sensor
P2271 = H02S Signal Stuck Rich Sensor 2

Repeating background info from a post to a different section hoping to resolve 2 issues...(1) being are both codes caused by an incorrect Catalytic converter or (2) just a bad part.

Kindly bear with for the below repeat (lengthy)

Background: Early 2022 the tail pipes "rear" of the muffler rusted thru/broke off. I took the Avalanche to a spot I had the exhaust replaced by 5 years earlier and simply wanted the pipes replaced "rear" of the muffler.

Unlike most, I walked outside when the truck was put on the lift. I watched as the mechanic first cut the pipe thru in front of the muffler and removed any other clamps, etc to the rear. But what struck me was when the dude walked to the catalytic converter and began cutting it free from the front. I stopped him and asked what he was doing and he gave a lame reason that I didn't follow thru with and new pipes were cut forward/aft of the muffler and all was installed "except for" the now missing 2nd catalytic converter.

Fast forward a month and a P0138 code surfaced (H02S Circuit High Voltage Sensor). I looked up under the truck and sure enough the catalytic converter had not been reinstalled so the spot was there showing the depression in the floor where it once was. I'm well aware folks that it is "illegal" for any shop to remove "without the permission" of the owner the catalytic converter. I cleared the code and drove the truck for a few more weeks due to having other vehicles it sat. The P0138 code resurfaced. I cleared it and drove to the muffler shop short short of PO'd and pulled the day manager aside telling him I was about to call in the troops. The Avalanche went up on the lift and the same mechanic that removed the catalytic converter half a year earlier feigned innocence and said "I just do what I'm told to do" and installed a converter.

September 24th, driving to town the check engine light came on.

Code P2271 (H02S Signal Stuck - Rich Sensor 2) came up on the Innova device in addition to P0138.


2009 Avalanche now has 229,000 miles on it. The codes in question could be due to age or a sensor.

My question is this by those who have actually experienced the P0138 or P2271 codes, what would cause the codes without my taking it to a mechanic as I try to do things on my own in my yard vs paying someone high fees.

Without clucking about the dude removing the catalytic converter months earlier, was the Avalanche designed to use a completely different catalytic converter than other Chevy trucks that was spec'd out just for the Avalanche?

If substituting a brand X converter would that throw codes or just the age of the truck and the higher miles??

Looking for quick help as I have never seen a P2271 code appear. Thx
 
1 thread is enough - thank you.
 
I'm curious if you're truck had original catalytic converters.
My 07 5.3LT 4x4 has two catalytic converters one on each side of engine exaust before they connect & route into muffler.
Previous owner of mine added a louder muffler for sound but I believe cat's both are stock.
I saw some aftermarket catalytic converters look like have a 3rd stage after merge together but I'd believe codes shouldn't notice as secondary O2 sensors would read b4 exaust gets thru 3rd stage.
Photos of my avalanche exaust might help?
I'd check o2 sensors & wiring to them, I hope shop didn't cut off catalytic converter from one side & not the other. I believe in switching both if one fails as other probably worn aswell.
Actual catalytic converters should have o2 sensors on either side. I hope that's not what they cut out, good luck hope you can sort it out.
 

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I believe these trucks designed for x2 separate catalytic converters, re reading your post sounds like the shop changed configuration trying use 1 catalytic converter?
I can't figure how wouldn't throw codes right away O2 sensors on one side or other should pickup cat missing.
They can get clogged up & soaking in laundry detergent I have seen cleaning them can help. From the sound of description sounds like shop did change your system not keeping it stock I'd verify they did it incorrectly & demand correction or claims court.
 
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