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GMC Yukon Reduced Engine Power message



  • chelsmithchelsmith Posts: 2
    Almost got stranded to with car telling me to service stability track and received reduced engine power message. I have also been driving this thing with basically two gears after getting it back from a shop that repaired a botch family member brake job. It won't change gears until after almost 4000 rpm then after that will not kick into overdrive and runs approximately 3000 rpm at 75mph. I took it to autozone when that started happening and they couldn't find a transmission code only a fuel related one. As of now engine power is fine but transmission issue is not. Seems more electrical than anything because of all the past issues. Dealership wants $50 to run scan and then $125 per hour to fix. This single mom doesn't want to be taken advantage of and would like some help from others on what the problems may be. I've read about possible wire harness problems and computer upgrades that may fix these issues? Do other shops besides the dealerships have capabilities of upgrading software? I'm in north Atlanta area.
  • jen1017jen1017 Posts: 6
    I really can't believe this....I originally posted here back in January with this problem..spent will over $1300 getting a new throttle body and wiring harness, had to take it back less then a month later because the gauges were going crazy while driving on the 6 months later and evening rush hour traffic on the 10 freeway in Southern California my truck 2003 Yukon goes through the reduced engine power abs light flashing, gauges going crazy, weird squeaking noise from the steering wheel, I'm back at the shop trying to find a resolution to the problem and hopefully its all covered under warranty!!!
  • jen1017jen1017 Posts: 6 the module and wiring harness they replace back in January came unwired..the spliced wiring came apart. Dealership that my shop towed it to acts like its no big deal that it happens all the time. I'm not convinced that this problem is not going to happen again, dealership doesn't seem to care and refuse to pay for the original tow to my shop and the tow from my shop to theirs. How is the tow my cost when it was their stupid part and splice job that came apart. I love my Yukon but really starting to think I wont own a 2nd one!!!
  • jen1017,
    We hope everything is going well with the repairs. If we can look into anything, please don't hesitate to get in touch with us at

    Sarah, GM Customer Service
  • Any0ne actuall file a complaint with the National Highway Safety Transportation Board? I just did it would be complaint 10473993.
    Oh has anyone actually tried to communicte with the GM customer service people? I think they are a fake entity they sound concerned but never get back on anything.
  • Good morning rongavaldon,

    When we look into the details of the different situations that the Edmunds community is posting about, we prefer to discuss the details privately as we do need to collect contact information and we handle each different concern on a case by case basis. Not to mention the excellent moderators of this web community would kick us out if we weren't legitimate.

    We can be contacted at if you would like to discuss any vehicle concerns you're having with us!

    All the best,
    GM Customer Service
  • In previous postings I have described my problems with Reduced Engine Power (REP)for the past three years - a summary:

    1- The original problem was caused by a rodent or squirrel chewing on the wiring harness in two different places which, as it turned out, GMC repaired with butt splices
    2- The truck ran okay for several months before the problem returned - the cable where it connects to the Throttle Body was replaced a second time by GMC - The Throttle Body was cleaned
    3- Several months went by and the problem was occurring on a regular basic - the Throttle Body was replaced but failed again within a few days - GMC wanted to replace the cable AGAIN - I said NO and ordered a replacement cable online and repaired it with good solder joints and shrink tubing - this was a much better job than GMC did on the two previous repairs - I learned MIL Spec soldering years ago and have not lost my touch - But, I am sorry to say the problem did not go away
    4- The Throttle Body was cleaned again but the problem remained
    5- I remembered the wiring harness was repaired by GMC in TWO places originally so I wiggled the cable at the 2nd repair and REP would come and go as it moved
    6- I took the truck to GMC but they wouldn't even look at it until I could get the truck there while the REP was occurring - moving the cable at the dealer would not recreate REP
    7- When REP occurred I limped into the dealer - WARNING: Do NOT let the dealer turn the engine off to read the mileage - give them an approximate mileage
    8- I showed the dealer where I wiggled the wiring harness again - it still would not cause REP to go away - I went for a test drive in a new GMC while they troubleshot the problem
    9- During my test drive the service department called and said they were replacing the cable to the Throttle Body AGAIN because of the computer codes read which INFURIATED me - I told them to not touch it
    10- We returned to the service department and smoke must have been coming out of my ears
    11- I showed the actual service technician where I had seen the problem - the service manager didn't even tell him about it - while I was standing there he took the wrap off the cable where the original repair had been made and said "There's the problem, it was repaired using butt splices, and should have been soldered according to the service bulletin."
    12- He repaired it correctly and it's been working perfectly ever since.

  • I bought a 2007 Yukon Denali a month and a half ago and it has been a nightmare with this thing ever since! First off, 24 hrs after we bought it the chrome back passenger door handle broke off. A few days later the check engine light came on. Took it to local GM Dealer and they said it was throwing the EVAP CODE, (something to do with the exhaust), quoted me 500 dollars to fix it. A couple days later slowed down to pull into a parking spot and it just died out of the blue! Immediately put it in Neutral and it started right up and run fine after that...For A Week. We took the kids outta town the next weekend and it was fine the 100 miles to our destination but on the way home that evening we were sitting in traffic for about 30 mins waiting to get on the interstate and it started Stalling. It ran fine on the interstate for a few miles then outta nowhere the Stabilitrak and Check Engine Lights started flashing. The computer screen read 'Service Stabilitrak, Traction Control On and Reduce Engine Power'. It went to shaking violently and lost all power. This lasted for about 10 miles then stopped and went back to running fine till about 20 more miles down the road and started again but this time it didnt go away. Eventually it started backfiring real bad. So we 'Limped' it as close to home as we could then had it towed home from there. Needless to say, we have a very expensive yard ornament now. I've read about this exact problem on a thousand different forums with a bunch of different 'fixes'. Anybody have this problem recently? And how much did it cost to get it fixed?
  • Good morning bethleann,

    We're sorry to hear that the Yukon you recently purchased has been giving you these troubles already! If you were planning on working with a GM dealership and wanted for us to look into this further with you, please send us an email at with more details, including: your name and Edmunds username, phone and address, the last 8 of your VIN and current mileage, and the name of your involved dealership.

    Sarah, GM Customer Service
  • Good morning,

    I have just experienced the exact same problem as message #480. 07 Denali XL 74000 miles. While towing a small load with transmission in tow mode (3 motorcycles, small enclosed single axle trailer) total weight aprox 2800 lbs on the hitch. Arrived at my destination 122 miles, let truck sit with load not attached. Re attached load started with remote key and when I put key in truck and put in gear and flashing on the dash Stabilitrak On, Traction Control and Check Engine Engine at Reduced Power. I let truck idle while in gear for aprox 50 yards. Stopped put in gear turned truck off unweighted hitch disconnected the battery & reconnected the battery twice. Started truck with the key this time and it ran fine for aprox 50 miles then displayed the same syptoms again. Repeated the process & it ran fine again until I shut it off 100 miles later. Lights are on again and this time wont go out.
    How much should I expect to pay the worst case scenario? ? ?
  • With the stabilitrk system it's hard to say how much, first start your truck, open hood and shake the wire harness in several areas, if that kills the motor then that's your problem, there is a chance if u keep driving this truck with this problem it may damage other parts, if u live in Illinois call Goodes automotive, I left info in my last reply. Gm knows this is a issue but won't take care of it, they told me its easier to try and sue them than do a factory recall, Obama gives our tax dollers to bail out gm, gm sticks it to us, I will never buy a gmc again, my 1996 gmc 2500 hd is so easy to work on ect. I've been a loyal Chevy gm man my whole life, from now on its fords.
  • svertheensvertheen Posts: 6
    edited September 2012
    Repost - my message was taken off for putting a phone # of the automotive shop, sorry to anybody offended

    Sorry if this isn't the right place. To all who have trouble with reduced engine speed, my 2004 Yukon sat for 14 months, the computer kept saying this was wrong, I fixed everything as it said was wrong, it was all bull crap, everything I fixed kept sending my truck into reduced engine, I almost caused a few scary accidents when I pulled out into traffic. Finally the truck security locked up my truck, wouldn't start, gauges flashing, I put a new throttle body, computer, pedal sensor, the other computer that controls door locks ect, mass air flo, everything electrical, it still went into reduced engine, there was only one thing left to do, I was so pissed off after 14 months, I left the truck running, I grabbed the wire harness to the throttle body ect. The truck died. There were 2 wires melted and the ground wire thinned out, what happened was there was a short in the system and it took out the computer, I didn't have to put all these other parts on but I left them on so I don't have to go through this again. During these 14 months after applying new parts it could run for 5 min to a couple of days before it went into reduced engine speed, it cost me over $4000 to do all this, check your wire harness first so u to don't go through this, and stay away from gmc certified mechanics, I took my vehicle to them and they played guessing games, I took this Yukon to 4 shops, gm mechanics this would of costed me about $8000. Mike Goodes automotive of Ottawa, illinois gave me good prices and will to anybody else, my truck was the first for him to figure out, so basically I was the lab rat, now this should be a cheap easier fix for other people. My Yukon started out to where It would go into reduced engine speed, I could pull over, restart my vehicle and drive normal. As time went on it got worse till finally it wouldn't start due to the security crap, I did everything I could possibly due right, it was tiring and frustrating. Now I been driving out of town far away with no problems, to many people including gm thought they knew what my problem was, gm charged me $900 for nothing
  • svertheensvertheen Posts: 6
    edited September 2012
    Worst case scenario depends who u works on it, I did some work myself and had it at a lot of shops, the gm dealer tried to charge me $900 just to look at it to tell me it was the throttle body which was just put on by me, I refused to pay and didn't, I took it to other shops and paid them a $100 each for advice and diagnostic, they all had different opinions, guessing games, it cost me $4000 ish to replace all electrical n fuel things except fuel pump. I went to Goodes automotive in Ottawa illinois because he was cheaper by the hour and someone I trust, this has been a experience for him, keep in mind I'm very experienced in working on cars, diesel equipment and small engines, everybody I took this vehicle to was confused, I had to stop working on my Yukon due to a major back surgery, I had to fix it because I couldnt get any money for a broke down yukon or dare sell my headache to someone else. I wanted it fixed so I didn't have to buy another vehicle and go through another nightmare. I also still had a loan on it. My truck still looks brand new so it was worth the $4000 I put into it. If you go to a gm dealer you would of spent $8000 for what I had done, I can't describe in words how difficult this was, I thought I was going to eat $30,000 Yukon and give up till I discovered the wire harness was also a big issue contributing to reduced engine speed. The wire harness gmc makes are garbage. Another thing to watch out for is where u go for parts, I like car quest, napa, advanced, some things from auto zone, oreilleys, ect. If u do go to gm you will pay 2-4 times more for a part than the places I mentioned, my mechanic was $70 an hour to where gm is at least twice that price or close to $180 an hour, I can't afford guessing games for this problem and parts from gm. I buy a manual on all my vehicles to completely tear down and rebuild. I needed help due to medical problems, it was nice to find the automotive shop I went to, there were times I needed parts for my Audi A6 Quattro. I needed new ball joints but you have to by the a arms complete, I found them for $400 and he found it and put it on for $$212.00, check your wire harness FIRST, then go to a autozone if that doesn't work and they will diagnostic the check engine for free, keep in mind 1 bad part can show multiple problems so it can be confusing where to start. I would of rather put in a clutch, transmission, engine ect instead of all I did for reduced engine speed, don't be fooled by shops for this particular problem, I would be happy to help any body with this problem if u like to face book me, Shawn vertheen, all my info to reach me is there, I don't want to give my email address or phone number do to them removing my last post, I understand why they did.
  • Good morning cinderrella,

    Sorry to hear that your trip was interrupted in this way. Were you planning on visiting your GM dealership for a diagnosis? There will likely be a diagnostic fee involved (which varies from dealership to dealership). Let us know if we can look into this further with you by emailing us at (include your name, contact information, and the last 8 digits of your VIN).

    Sarah, GM Customer Service
  • I filed a complaint with the National Safety Transportation Board.

    My truck is a 2007 Yukon XL, bought it new. Nothing but problems.
  • This is the beginning of my story, I was 45 min from home when my door looks flickered on n off, gauges flashed acting weird, I had to pull over due to no power, the pedal could be all the way down and no power, reduced engine speed. I turned the truck off then on, made it home no problem, for the next 4 months it just kept repeating, turn truck off then on and good to go, the problem got worse, it got to the point I couldn't drive it a block, I went through everything and I could not figure this problem out, I was the type of guy to drop a transmission and put a clutch laying on gravel, took it to shop 1, they said o it's the throttle body, so I fixed it, still went into reduced engine, then they said it was the PCM, I had that fixed, same thing, shop 1 couldn't figure it out, I was trying to avoid a gm dealer cuz they are 2-5 times a part and 2-4 times in labor, they diagnosed the truck to tell me it was a throttle body and pedal sensor, they tried to charge me $900 to tell me something that wasnt true. They are the reason i started working on cars 17 years ago. I have restored cars from the ground up, I was angry, gm Chevy mechanics in my experience think they know it all, I put a new pedal sensor assembly on, still went into reduced engine, I took it to shop 3, that guy didn't waste my time with his opinion, he said sorry I can't figure this out, my computer was saying this was wrong when it wasn't, I know cuz I just fixed those issues. He told me I should trade it in but I woulda lost a lot of money, or do I want my problem to be someone else's problem. Finally after 9 months I took it in to a friends shop, took all the new parts in and got new ones. Still didn't work, my truck locked up, the truck wouldn't even start, after weeks of playing around I had another computer put on, started right up. It still went into reduced engine speed, I lost a lot of sleep over this.............. I had a gm tell me it's easier to sue them than do a factory recall, they admitted that there is a problem. I came to this website a year ago, I fixed everything that could cause this except the wire harness, that was my last step, sure enough when the truck was running if u grabbed the harness the truck died, the wire harness had 2 melted wires and the ground was thinning out, that finally fixed my truck, I fixed so many parts even stuff I didn't mention, I spent $4500 but that included new tensioners, belts, trans filter changed, differentials changed, battery, synthetic oil changed, new rear wiper motor, new computer, new PCM, pedal sensor, mass air flo sensor, air conditioning pump, brake pads, rotors, calipers, 1 wheel hub assembly, a new ignition, fuel parts, fuel filter, 2 bolts drilled n tapped on exhaust, ect ect, if u went to a gm dealer that would cost u well over $8000, Goodes automotive in Ottawa Illinois did all that 4 me while I had my back surgeries, it was worth it, if I bought a new vehicle I would go through all this eventually, now I'm back to driving my 2004 Yukon out of town. The truck looks brand new, I was afraid to drive before this got fixed, I didn't want to be stranded with my kids far away, the way I see it is this should be cheaper for other people since this was a first experience for them and me as we'll. I think if I caught the short in the wire harness first I wouldn't have had to replace all this extra stuff. I have never experienced anything like this in my life, I used to do complicated things on cars before, I used to work on diesel equipment, restore cars, install audio systems, the boss at work for land development, use the GPS, grades, blue prints, I just received a large amount of $s I will by a ford now or anything but a Chevy gm.
  • I beg anybody to please check your wire harness when reduced engine happens, even if u have to grab the throttle body harness and shake it with the truck running, if the truck dies or idles weird then that's your problem. I just don't want to see this happen again to people, very very dangerous to drive with reduced engine. There is to many shady shops out there today and gm dealers, my friends that were gm techs, some didn't graduate or just finished there diploma, if gm likes you they put u through school.
  • Exactly where is the wiring harness?
  • I tried your so-called email and it failed. I dont think you are for real. My email is I will corrispiond that way. By the way I am still haveing the same Reduced engine power mode problem. and have since taken our vehicle in to the dealership ervery other week since May. still no fix.
  • Ive tried that, and still no sucess. I dont like the way the harness just hangs there too much vibration could render the harness trash. Still having REP problems.
  • Started having this problem on my 07 Suburban today. Shut it off and it runs ok now, but check engine light is still on
  • Good afternoon jamendolare,

    Are you planning on working with your dealership to get this looked into? If you are, and if you wanted for us to check into this further, please contact us via email at (include your name and Edmunds username, phone and address, the last 8 digits of your VIN and mileage, and the name of your dealership).

    Sarah, GM Customer Service
  • This is a joke. GM does a recall because of 4 accidents on 4 vehicles....I was in an accident due to reduced engine power and on this message board ALONE you see the dangerous hazard this has caused. My vehicle has been parked for ONE YEARbecause no one will help and I am still paying for the junk.and it does not run AT ALL. I would love some support from GM.
  • Have a gmc denali 2005 have taken it back to dealer 2 times first time lost of power came on my wife and kids were in the car on freeway when the car lost power and they were trying to change lanes had it told to dealer they said loose connector repaired the car in about 3 hrs about a month later driving pass school when it say lost of power and turns off the hold time no power steering or power brakes trying to avoid kids the dealer came out towed the car in cause it was the same problem they said would be ready in a couple of days they called me in about 4 hrs and said it was ready so the next morning me and my wife picked it up and ask what was the problem they gave me same answer asthe last one.Not to be confuse i bought this car used from honda dealer the first incident car was still under 90 day warranty i told them each time how this doesn't seem safe for me but more so my kids and wife and they insured me it was safe now but to weeks later the same thing happened to my wife on the freeway highway patro had to help here get out of fast lane and to the side of the freeway safely.Sad to say but someone most likely traded the car in and honda sold me a lemon which is unsafe because if gmc can't fix it how can honda any ideals on how to deal with this.
  • Good afternoon piznope,

    Is the dealership you've been working with one of our GM dealerships? If so, we can check into this further with you if you like. Please contact us at with more details (include your name and Edmunds username, phone and address, the last 8 of your VIN and mileage, and the name of your dealership).

    Sarah, GM Customer Service
  • I go to pick up my denali this morning which as from my previous post under piznope has been having problems had to make a new post cause couldn't sign in for some reason but all that aside they have had my car for 9 days at the honda dealer where i purchased it from they tell me come pick it up they can't seem to find any problems with the car they said they called the chevy gmc dealer and they said until it does it again theres nothing they can do now.Can you say scared to death this is my only car right now and i'm going to or should i say have to drive it but i won't let my wife drive it bettr me in this car than her when this happens again once again i did purchase my car from the honda dealer used not gmc but i also called gmc yesterday myself and ask they said the same thing if i could get rid of this car and get something else i would but i can't right now .So i'll have to drive my wife where ever she has to go and wait till this happens again.I must say one more thing if the honda dealer would of put it on diagnostic machine the first time or the second time instead of shaking wires and cleaning connectors i might of had a safe car.Piznope
  • Yes, it happened again. four times in the same day, and then again the following day. When i shut it off and wait a few mins. it resets and is ok for a while, but it is getting worse.

    Wanna start a class action suit?
  • What i tend to notice is alot of people are buying used denali ,chevy or gmc on this post like me and it seems that the previous owner or maybe try to fix the problem or maybe they didn't and just trade the car in and now there are alot of unsuspecting people buying these car which and getting left with this problem and it is a safety issue which i'm now finding out myself and i am working on trying to get out of this car and hope if this happens that they don't sale it to someone else.I feel that gmc should a flag or warning post so people don't have this problem because it will not make the company look good if they don't show some true concerns.Just saying gmc\chevy do the right thing other car companies have done this sad part is there mostly foreign companies.
  • what else i got to loose
  • I bought my new, it had less than 200 miles on it. 2007 Yukon XL. GMC/Chevy won't do anything. I am not sure that I would even trust them at this point to fix the numerous problems with my truck. I have tried to get help through this forum, the dealerships and GM service. They simply don't care that people are having these problems and are hoping that most people don't check these forums before they purchase their vehicles.
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