2003 Yukon XL Reduced power issue -HELP!

[Kd32]

I have a 3/4 ton 2003 Yukon XL with a 6.0L that I bought new. In Oct 2008 we started noticing the smell of antifreeze and eventually the truck went to reduced engine power and said to add coolant. I took the truck to the dealer that I bought it from and had it exclusively serviced at, and they concluded that I needed a new water pump and head gasket. $2500 later, I took it home and a few days later it went to reduced engine power again. I returned to the dealer who ran pressure tests on the radiator and they said it wasn't the problem. I asked them why it would keep going to reduced engine power and they said they didn't know and sent me home. I started going to reduced engine power on a daily basis, so I ended up getting a code reader. I recorded the codes and then erased them because my truck would only idle at reduced engine power- 5mph max. I went back to the dealer with the codes and they said there was nothing wrong...codes had to be present. Codes were P2135 and P1516. I researched these and after the dealer once again told them I wanted the throttle body assembly and wiring harness replaced and took along the detailed TSBs for them to follow. The service manager told me they couldn't do that because the truck was not currently producing the codes and that I would have the produce the truck with the codes present. I live 30 miles away from the dealership and have to use busy highways and interstates to get there, I could not safely idle at 5mph for 6 hours to get there. Lucky for that service manager, she went to lunch and I talked to a new service advisor. He told me he had seen lots of trucks with the same "reduced engine power" issue and replacing the throttle body and harness usually fixed it...so for $800 they replaced them.

Ok for a few months....then I start getting reduced engine power with the same codes again. I erase the codes and log them, hoping to find a pattern to present the dealer with so I can take it back in. I took it to a dealer closer to my home, mind you I had erased the codes, but had presented the service dept with them. This dealer was kind enough to give me a loaner and drove the truck themselves a few days hoping to go back to reduced engine power. After 3 days and no code, they sent me home with the truck. Next day it went to reduced engine power for me and I limped my way back. They said the wiring harness had not been spliced onto the throttle body correctly and I needed to replace that. Luckily I had only put 11,800 miles since the first one, so I did not have to pay for the part, only labor.

Went another couple months (mind you I don't drive the truck without the code reader now!), we were pulling out with the camper and DING DING DING Reduced Engine Power again. Noted the same P2135 code, erased it and drove home without issue. Every week or so I would get reduced engine power. I would erase and forget about it.

This past winter it started more frequently AND the truck would stall when it went to reduced engine power. I would lose all power steering and braking and almost got in a few accidents. Finally in February I took it in (with codes P2135 and P1516) and they said it was a ground. Replaced it for $150 and went home. Couple days later....Reduced engine power again....back to the dealer.....this time they said it had to be that wiring harness, so they replaced it again....$500...back home a day and now the reduced engine power again. This time it is additionaly throwing codes P0120 and P0220 in addition to the always present P1516 and P2135. Truck has been in the shop for almost 2 months now. They have inspected all the wires, checked voltages, replaced terminals and grounds, replaced module under the dash and it still goes to reduced engine power. I asked the service manager about the pedal position sensor and he said the codes they were getting weren't suggesting that.

The dealer said GM is not giving them any support, just telling them it has to be the throttle body and harness. The mechanic at this point has personally inspected every wire on this thing and I know he is just as frustrated as I am.

I can't drive this truck anymore as it stalls as soon as it goes to reduced engine power. I can't sell it knowing it is a huge safety hazard. Does anyone know what the cause of this could be?

Thanks for any new insights!!

[linton23]

I doubt it would help but I had a 2005 Trailblazer that I drove to deliver to a customer. The trip was over an hour and no problems the customer gets in to drive it and bing reduced power light comes on and the car drives bad. I get in to drive it and nothing no light or anything. I start to drive it back and I get about 10 miles when bing reduced power mode kicks in. We get it towed back to my dealer and a wire plugged into the transmission was loose. As soon as its reconnected it drive fine. A day later I take it back to the customer they buy it and everyones happy. They say its a harness maybe its just not the one they think it is.

[Jedi]

You brought codes and tsbs to a shop? haha, no wonder they ignored ya. But it seems like they dont want to help you, go to the next GM dealership.

[Backlash]

Sounds like the only part of that system that has not been replaced is the APP sensor(which would cause these codes) and the PCM. With what you have spent so far, I'd gamble and ask them to replace the pedal sensor(APP sensor).
We normally drop a little solder on each terminal as well but, I see you've had the harness replaced twice already.

[Kd32]

I only took the codes and TSBs after I had been there twice and they insisted there was nothing wrong with the truck. They refused to even inspect the wires because no codes were present.

[73ChevelleSS]

There is a ground on the rear of the drivers side cylinder head.I have repaired several of those codes by repairing it.If you give it a tug it will probably break.I think it is ground #G110,but I might be wrong.

[TruckMan]

After spending all that cash at the dealership, I would trade it in on something else. Tell them that if they think there isn't anything wrong with it, then they should give you a decent trade-in value.

If you insist on keeping it, then tell the dealership that you're not paying any more labor costs for their incompetence. I would never pay for labor on something that didn't fix my problem. Well, maybe at a local shop, but not at a GM dealership.

[bmcconn]

First of all, sorry to hear that you are having problems. But to make matters worse, I don't know if having the codes active and present, would actually make a difference!

I drive a 2006 Pontiac G5. Just recently, it started going in to Reduced engine power, meaning that I was and STILL am not able to accelerate.

Anyways, the mechanics at my local delarship gave me a similar sotry: "If the car wasn't in reduced engine power at the time, they couldn't tell what code it was and therfore were unable to idenitify what the actually problem was". So as a shot in the dark, it was reccommended that I replace the pedal accelerator, which I did. All but gtwo days late, reduced engine power yet again.

However, THIS TIME, when it went in to reduced engine power I was close to the dealership and actually took it in and left in running so that the mechanic could sit in it. Anyways, after a codes test, it was then determined that I needed to replace my ECM. This was done, and no less then a week later, reduced engine power AGAIN.

I took the car in, and the mechanic literally shrugged and said that GM mechanics have no idea how to fix this problem, and actually suggested that I trade in for a new car.....

From what I have been reading, this "reduced engine power" is a serious problem for GM - one that warrants a recall.

I hope I added some insight - and if anyone has any suggestions I would love to hear from you! Right now I stuck with a 4-year old lemon in my driveway

[sirletters]

For the 2006 pontiac g5 make sure fuel level is at least 1/3rd. If problem persists check to make sure your fuel sending unit is functioning properly as this reads fuel ammount left in gas tank. Once the fuel is read as very low the car will go into limp mode so it can be crippled to a gas station. In any case get it covered under warranty and get them to remove tha gas tank and change it out. I'd be startin' there.

[effingpsssed]

When as a society will we wake up and understand that all of these emissions and electronic crap on our vehicles is not helping? I'm effing pissed. First it was the crappy Ford diesel that I unloaded to get a GMC 6 liter gas motor for work. Now after 4 thousand miles it keeps turning the "reduced engine power" trouble light on. I'm done. I'm looking for a pre-smog truck that was built when America was proud and united. Not this union run lazy arsed mobbed up crap we have now. Good luck America

[jmike11]

I have a 2003 Yukon Xl 1500 5.3 engine. For about the past 4 months I've been having a problem with the "Reduced Engine Power" light coming on. It was happening randomly and frequently. I took the truck to Auto Zone and had them run a simple diagnosistic. The problem code that they found was "p1516" so I had them print it out. . According the code this meant there were several possible problems. They all fell under the heading of "module throttle actuator position performance". The print out when on to further list the following: 1( poor connection at the TAC module, 2) Failed TAC module, 3) Check TPP or TPS sensors, and 4) Binding or bent throttle plate-fail throttle body. So I when around to different mechcanics and parts stores tring to fidure out just what the problem really might be. I also been reading the forum comments and took heed to them especially the ones that discuss the "reduced engine power" problems. So armed with knowledge and confidence i put a new throttle body on myself. I drove the vehicle about 20 miles and it started doing the same thing. So I took it back to again the the local parts store and had them reset the computer. Now its working fine. After you have work done you should reset the computer because it doesn't recognize that you've had work done and it doesn't reset itself. So have it reset and see what happens. All the best jmike22!!!!!

[jmike11]

After all the work you had done did have the computer reset? I put on a new throttle body and it worked fine for about thirty miles. Then the reduced engine power light came back and the truck started doing the same thing. So I took it to one of the "local auto parts stores " and they reset the computer using the diagnostic units they have, it works fine now "so far"! Try having your's reset. Good Luck!!!