2004 GMC Sierra "reduced engine power"

[bradshow]

It's been a while since I've been on the site and I hate to come back now just because I have a problem but at this point I have no where else to turn.

I'm supposed to drive to Texas to pick up my daughter and take her back to Kansas tomorrow and driving my truck into work tonight out of the blue the truck went into "reduced power" mode and the SES light came on. The truck still runs fine or appears to run fine but there is no power while driving, like I have 50 hp available.

I pulled over and popped the hood, nothing appears to be loose and my only mods are a CAI, which I wondered about because the intake tube sits on the upper radiator hose and it was very hot.

I plan on going to Orielly's first thing in the morning to run the codes and from what I've read on the net so far is that the TPS sensor is a common failure on these trucks and that in order to replace it I need to replace the entire throttle body. The local Orielly's online site say they have one but there might be a "relearn procedure" invloved. Anyone know what this procedure is?

Any other tips or info would be greatly appreciated and I know not having the codes is basically blind science but I want to get a jump start as I have to leave town at noon tomorrow.

[BMR Sales]

Find out what the check engine light is, that will be the key to figuring out what is going on otherwise we are just wasting time. I am really familiar with those truck since I have one of my own so once you figure what the check engine light is I can probably help you out.

[rjones916]

I've seen a lot of problems with the throttle bodies and connectors, if you replace the connector make sure you solider the connections because if you use just regular pink butt connectors it will happen again, i've been there lol...gotta pull the codes and start from there though...Also btw, coolant runs threw the throttle body so you will loose a little bit...No relearn procedure needed, just need to clear the codes, if they don't clear that wasn't the problem, there is also a TAC module in the circuit that controls the throttle body and accelerator pedal....Good luck

[WickedMom]

I suggest unplugging the TB and inspecting the connector & pins. Sometimes water can get in there and cause corrossion which doesnt happen right away

[Bill Brollier]

Brad:

Do you need to just come by my work place and borrow my G8 to pick up your daughter?

Call me if you do.

[bradshow]

Well this morning was a mad dash.

Got off work at 6am and went to start the truck still had the SES light but full power.

Code was p1125. Cleared it and no issues on the 100 mile drive to tx.

Started driving back and as soon as I hit the interstate. SES and reduced power.

Drove to autozone and bought a scanner. Same p1125 code.

Cleared it and am currently driving back to okc.

Any ideas?

Bill, thanks for the offer. Hopefully I can get this fixed


Sent from my iPhone4

[Seattle09GT]

A check of the internets - P1125 with Reduced Engine Power indicator on GMC Sierra GMT800 and GMT900 platform.

Potentially bad Accelerator Position Sensor (APP). The triggers that will set off this OBDII code are:

DTC P2108 or U0107 are not set
The ignition is in the Crank or Run position
The ignition voltage is more than 5.23 volts
DTC P1125 will run continuously once these conditions are met.

This means:

1) Both APP sensors are out of range OR
2) Both APP sensors disagree with each other OR
3) One APP sensor is out of range and the other sensor disagrees and
4) The conditions occurs and last longer than 2/10 of a second

If you clear the SES code with a scan tool the vehicle remains safe to operate - until the code appears again - and then you'll have to reset again. Get reduced power while trying to scoot through a tight intersection and bad things could happen.

Resolution, likely you need to replace one or both APP and/or replace the Throttle Actuator Control Module (TAC). Apparently there are some TSBs out there on various GMT800 and GMT900 vehicles with this problem.

[bradshow]

Any idea how hard it would be to replace those sensors?

I found that same page but not sure it's wise to drive and surf at the same time. Lol


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[GRRRR8]

9 out of 10 times it is the throttle body causing your issue.

[bradshow]

9 out of 10 times it is the throttle body causing your issue.

Probably just gonna buy one then. Thanks.


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[bradshow]

Changed the throttle body and the MAF. Still getting the code above.

I guess I need to change those other sensors?


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[rjones916]

Did you look at my post earlier?

-Ryan

[bradshow]

Did you look at my post earlier?

-Ryan

My connectors and wires look really good. They're not discolored or brittle. Can I buy just a new connector?


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[bradshow]

Final fix was replacing the entire gas pedal assembly FYI


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[Bill Brollier]

Glad you finally fixed the problem.

[GT Drew]

Code P1125 is the code for the accelerator pedal position (APP) sensor. You confirmed the wiring and connectors were not broken. Why you replace all the other items, just a waste of money.

[Chris14]

I also have a 2004 GMC Serria 2500 6.0L and have had this p1125 codes so many times. I first started replacing the APP. The problem would go away for a week or 2 and would come back with the same code. So then I replaced the throttle assembley and would fix it again for just a few weeks. I was using aftermarket parts so then I went to my GM dealer and replaced both with GM parts. Problem gone for awhile then came back. I guy at the dealer said to replace the wiring harness at the throttle body and at the APP switch which this harness goes from the APP directly to the TAC Module. Still had a problem. The only other part left in that system is the TAC module so I replaced it with a GM part. Problem would still come back when you least expect it. Anyone have any help on what should seem to be a simple fix?? It seems like sometimes when you hit a bump just right it will set reduce engine power????