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Discussion Starter #1
Hey guys - so I was researching this code on this site and there are about a gazillion different entries for this particular code. "Engine Overboost Condition" Most of the posts say the MAF sensor is the issue. I brought it to the dealer today to get some PM done and when I told them about the code and that I'd like the MAF sensor looked at they didn't seem to believe me.

My situation in particular is that I was climbing the Green Mts of Vermont and I'd be moving along at 65-70mph with my 14,000# 5th wheel attached. I'd go to pass, the truck will downshift into 3rd start to take off and then almost go "limp" for a few seconds until it slowed to about 50 and then it would pick back up.

When the dealer told me that everything was fine with sensors, etc I asked them what would cause that code to pop and was told that the 4" exhaust I installed is causing it. I know plenty of people that have installed new exhaust on a truck with an LB7 and didn't have any issue.

Any other ideas? The fuel filter was changed today just in case and my air filter is clean.

Thanks!
 

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bump! id like to know myself
 

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Has it happened since you changed the fuel filter?
 

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mine is doing the same thing. i got the truck it was stck i put 5'' exhaust on it 2 days after i got it chaninged the stock air filter to another stock and the oil and fuel filter and i pulled a heavy load with it and it started kickin into limp mode. same thing that is goin on with this guys. i have heard that it could be maf scencor, fuel filter, bad ful line, bad injectors, weird shifts in trans, weak injector pump, short in a wiring harness by altanator, turbo wastegate actuator... list goes on.. im lost
 

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Ive got over 20K with a 5" system and have never thrown a 234 code.
 

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Keep in mind DTC coding is generic. A P0234 is the same description for every vehicle. Its overboost. Just what it sounds like. The engine is getting more boost pressure than desired.

Assuming your turbo is stock, it isnt variable geometry. So you dont have that to worry about. It could be as simple as a wastegate issue. But to the OP if your getting a P0234 code, it is definitely boost related. Dont worry about the fuel filter and stuff (well u know what i mean). Logan - dont confuse limp mode with OP issue. Many things can cause it.
 

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Keep in mind DTC coding is generic. A P0234 is the same description for every vehicle. Its overboost. Just what it sounds like. The engine is getting more boost pressure than desired.

Assuming your turbo is stock, it isnt variable geometry. So you dont have that to worry about. It could be as simple as a wastegate issue. But to the OP if your getting a P0234 code, it is definitely boost related. Dont worry about the fuel filter and stuff (well u know what i mean). Logan - dont confuse limp mode with OP issue. Many things can cause it.

If you fueling is off it will set this code as well, not a lack of pressure, but a "lean" spot in your tuning. If the truck does not have a tune of any kind, I would follow the diagnosis flow chart.

This is a pretty old thread someone dug up.
 

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I dug it up :D Just couldn't find anything on it. Thanks for the help what you said makes sense it was just overfueling assuming stuck injector and then sensed overboost compensation I guess you could say cause of the extra fuel.
I'm not gonna worry about it.
 

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I dug it up :D Just couldn't find anything on it. Thanks for the help what you said makes sense it was just overfueling assuming stuck injector and then sensed overboost compensation I guess you could say cause of the extra fuel.
I'm not gonna worry about it.

Not quite. More like to much boost or not enough fuel. I'm not really sure how to explain it without copy and pasting verbatim out of the repair manual.

Essentially, Accelerator pedal position, Fuel in MM3 and Manifold pressure all need to be at certain values for the ECM to decide its an overboost condition.
 

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Discussion Starter #12
I actually traded this truck on a 2013. Injectors were starting to go and I didn't feel like messing with it. I do miss the fuel mileage and the growl of that old LB7. Eventually I'll delete mine and be happy again. :)

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