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Discussion Starter #1
I have 2012 C2500 Diesel and tow an 8000# camper trailer regularly. When I tow I use my exhaust brake. I have just over 122,000 and I purchased it in February of 2015 with 44,000 miles on it.

This truck has gone into LIMP mode three times and all three times it required an O2 sensor replacement and manual regen.

I know that this can't be normal. By using the exhaust braking is this effecting the O2 sensors?

I've been out of mechanics for over the last 15 years and retired. I'm just tired of tying up traffic while I am towing, so be kind to this old man.

Thanx in advance:
 

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Are you sure it wasn't NOx sensors (there are 2 of those).

In any case, I don't think the eb has anything to do with the problem.
 

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Discussion Starter #3
I'll have to check the invoice when I get back to the office tomorrow.

Thanx for the reply.
 

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What are you calling "limp mode"?

Engine limp...Rpms capped at 2,000.

Transmission limp...Stuck in 3rd gear.

Oxygen sensor (NoX)...Speed restriction incrementally 65mph, to 55mph, to 4mph, all indicated on the DIC.
 

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Discussion Starter #5
Speed restriction incrementally 65mph, to 55mph, to 4mph, all indicated on the DIC.
 

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I've got an old LBZ and it went into limp mode towing similar weight. Went thru fuel filters but problem came back. It happened on hot days after idling hot for a while, tried to get going and 2K rpm and not upshift, 30mph. I could pull over, do a cool down for 10min and then restart but problem would returnn on hill. Since then I added a lift pump. I think the problem was part of fuel hose was soft and it collapsed with fuel demand. The problem has not returned so I am hoping the lift pump fixed it but who knows.
 

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Are you running any kind of additives in your diesel? Wondering if something is polluting the sensors over time.
 

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Discussion Starter #8
I've got an old LBZ and it went into limp mode towing similar weight. Went thru fuel filters but problem came back. It happened on hot days after idling hot for a while, tried to get going and 2K rpm and not upshift, 30mph. I could pull over, do a cool down for 10min and then restart but problem would returnn on hill. Since then I added a lift pump. I think the problem was part of fuel hose was soft and it collapsed with fuel demand. The problem has not returned so I am hoping the lift pump fixed it but who knows.
My problem is that I have had 3 GM 12671387 Sensors (Nitrogen Oxide) replaced. I would like to know what is causing them to fail. I do drive with my engine brake on most of the time.
 

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It was very common for early LML's to need one or both NOx sensors replaced. So common that there was a special extended warranty program to cover the costs.
 
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Discussion Starter #10
It was very common for early LML's to need one or both NOx sensors replaced. So common that there was a special extended warranty program to cover the costs.
Thanx:
Is there a TSB or letter that references this?
Thanks again:
 

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Search on here should find it.

iirc, it was seven years or xyz,000 miles. Unless it's 'new vehicle delivery' date was delayed the truck has likely timed out.

Search the 'NOx sensor' and/or 'DEF poor' threads.
 
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