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GMC Yukon Reduced Engine Power message



  • Just wanted to alert everyone to another thing to check besides the Idle Control Wires and contacts. My 2003 Yukon XL had quit several times too by loosing power right in the middle of 70 mph on the highway. Received the Reduced Engine Power message on the last time it quit. While looking for a dealer to take my truck to I found this forum, which gave me a clue for my mechanic to look at. Here's the deal. In addition to replacing your Idle Control Body you can also have your mechanic take a loose the idle control body and check to see if it is clogged up. My idle control wires and contacts were fine. However the control body itself was extremely gummed up over 4 yrs of wear. My mechanic took it apart and used some carbuerator cleaner to thoroughly clean it out. Put everything back together and I have been good since. Cost me a few dollars for an hour worth of his time.
  • Hey Bonddog,I dont want to burst your bubble on this but being a tech, and being very familiar with these issues,I just want to say that an Idle control valve does not have the capabilities of making the reduce power message come on. It is strictly for an idle control of the engine,the reduced power light and I have worked on this problem several times is usually caused by rust build up under the front abs sensors....I suspect that you will see your problem re-occur. hank
  • Alright here is my latest. After this thing died and I could not get it going again. It was stuck in reduced enging power I finally had to make some drastic moves.
    The dealership wanted to replace the tac module on the firewall. But after I thought I had fixed it when I replaced the brown and yellow wire ends that connected to the trottle body and had 2 months of success I fiqured it had to have something to do with that. I ended up replacing the throttle body. The cheapskate in me found one in a junkyard on a totaled out yukon. It cost me 175 shipped to the door. Replaced it in about 20 minutes, and it fired right up. Runs like a champ.

    I am hoping this solves the problem and not just another teaser for a couple of months.
  • Did you disconnect the battery for any reason during the swap-out ? If so this may have cleared out the code and started back up with no problems after the code was cleared. Hopefully you have fixed your prob. I still have not had any trouble with mine since i replaced the harness. Sounds like there is about 50 things that can make the Reduced Engine Power. lol

    My wife called on her way home and had the "REDUCED ENGINE POWER" message and the check engine light was on, 2003 GMC Sierra 1500, she did not think she would make it home, just a few blocks away. I checked the net and found this post and started checking at the battery and almost right away found that the negitive battery lead was not tight where it connects to the block, it was not arcing loose, just not snug, a 1/2" wrench to thighten the bolt and the engine idle returned to normal, the message and check engine light is off and it drives normal. Thanks for the help!!!
  • I have an 07 1500 Sierra Classic with the 4.8 that just started having this problem. The first time was just before thanksgiving but after shutting it down it fired up and ran right so I just pulled the codes and they read that the TPS was "out of range". The check engine light turned off after messing with a few things: gas cap + intake. The thing is the problem just resurfaced again. I've got an appointment with the dealer as its still under warranty. From the sounds of things they are going to jerry rig a fix so can anyone provide any info that might help save me from constant trips to the dealer? :(
  • it seems that everyone is talking about yukons. my son has a 2000 pontiac firebird with a 3.8 liter v6 engine. he has had the car for 16 months. he had problems with the engine so i bought another 3.8 v6 and now we are seeing the "reduced engine power" light come on. what gives? :confuse:
  • guys, after sifting through many posts and many different forums (like i have come to this conclusion:

    -Replace wire harness to throttle body (get the AC Delco OEM harness) probably

    This is from GM:

    The PCM detects that the commanded and actual throttle positions are not within a calibrated range of each other.
    The above condition is met for less than 1 second.

    Step 1. Tighten ground G103 located next to the right cylinder head (passenger side) just below the head and mounted into the block. The ground uses a 13 mm bolt head mounted vertically to the engine block just above the bell housing. G104 located behind the left cylinder head has also been found to cause this concern.

    Inspect throttle body torque. If the throttle body is improperly torqued to the intake manifold, remove throttle body and retorque the throttle body mounting nuts per SI in a two step process: 45 lb. / inches. on the 1st pass, and then 89 lb. / inches on the final pass.

    Verify all electrical connections especially right at the TAC module. There have been reports of the plastic retaining tab in the connector missing causing poor contact especially on rough roads

    Road test vehicle to determine if code re-sets/condition re-occurs. If not return it to customer.

    Step 2. If condition is not corrected using above procedure, or re-occurs, replace throttle body assembly.
  • In regards to the person with the 2000 Firebird ---

    I didn't know that car came with a Driver Information Center (DIC). Are you sure you're just getting a "Service Engine Soon" light or can you actually read, "Reduced Engine Power"?

    Those cars didn't use electronic throttles, at least I didn't think so.
  • I have a 2003 Yukon XL Denali the Traction Control Light comes on the the Message Reduced Power comes on the it stalls and i can stop and restart it will run fine the rest of the day. Is there any new suggestions is it still ok to drive or need a immediate fix. This has just started since it has got cold and i nedd to put brakes on the rear could this be part of problem
  • bmcgbmcg Posts: 1
    Exact same problem just started for me for me...On startup, Traction Control Light comes on and the message Reduced Engine Power comes on. Engine is limited to 2000rpm. The 1st time this happened I shut the truck off, turned it back on, and it's fine. Other time I tried 3 starts with no luck, an hour later...I tried it again, and it's fine. Vehicle is an '03 Escalade. Any input would be appreciated, Thanks
  • Well i have finally solved my problem we replaced the throttle body and the wiring harness and took all grounds loose sanded them the tightened them back. I got this from a message a fellow left on this site and it worked for me not had this problem for two weeks and i was having it daily.

    Thanks to all
  • I cannot thank you enough for taking the time to post all of this information; I especially appreciate the photobucket picture, so I could locate what everyone was talking about. I went outside immediately, gently wiggled the wiring harness, restarted my 2003 Chevy Suburban... the REDUCED ENGINE POWER message was GONE... okay the engine light icon is still on, but I can drive my car now to the parts store... and thank you also for providing the part info and numbers and pictures... this has saved me a bunch of additional time...

    I thought we were going to be involved in a horrible accident today on the highway... YES, this happened on the highway and we had an 18-wheeler baring down on us with no where to pull off... I did have the forethought to put on my hazards, and most people were able to change lanes and pass us... but the 18-wheeler could not move over, and for some reason was refusing to slow down at a more reasonable speed... he was inches from my bumper before he finally changed lanes... I had 3 of my 4 children with me, all under the age of 5 in carseats... I was so scared...

    I cannot believe GM has not recalled or addressed this problem proactively... They will be hearing from me via certified letter...

    So thank you EVERYONE, but most especially, you... you covered all the bases for us... and lastly, I'm sure you saved us a bundle of money, something we cannot afford to be frivolous with these days...

    Laura (mom2four)
  • moe1954moe1954 Posts: 1
    I have a 2004 Yukon. My engine light has come on about 4 times sense I bought the thing. I keep taking it back to the dealer and they run dynostic on it and say that the fuel cap is not put on right. The last time I went there they put a new cap on it but the new cap goes on to easy and it dosn't seal good. It dosn't have the same seal in it the last cap I had, and now the light is back on. I guess I will put it in the repair shop if you cannot help me with this. I don't know if I should keep buying fuel caps or is there some wiring somewhere I can check. I don't know where to locate this. Thank you.
  • rshtrsht Posts: 277
    Not sure if you still have the old fuel cap? Some times the pressure relief valve inside the cap may be partially stuck, use a paper clip to gently push (through the little pin hole in the center of the cap) on valve to make sure it moves smoothly; as far as the cap seal (if you still have the old one), I would clean the seal and its contact surface on the filler opening. If all failed, personally, I would then hook-up an ODB-II scanner (your local AutoZone store can do it for free if you don't have a scanner) to see what is/are the trouble code(s) that associated with the Check Engine light... If the problem is with the fuel cap, the Check Engine light should go off fairly soon after the cap is on tight (~5-clicks...).

    Just for reference, one time I left the cap off, my Check Engine light came on before I was even out of the gas station parking lot. After I put the cap back on, less than a mile, the Check Engine light went off by itself...
  • flex4flex4 Posts: 1
    i have yukon XL 2001 model some time when i drive a car showing message REDUCED ENGINE POWER so you can help me on this :confuse:
  • rshtrsht Posts: 277
    Have you had the chance to read Message #22 from "bunchz71" on this topic of discussion? He/she posted a link to a picture on where the bad connection was that caused the "Reduced Engine Power" message. Your Yukon is a couple of years older, so the position of the wires/connector may be in a different location.. Hope you locate the trouble maker easily with the information from this forum.
  • This morning I went shopping, came home everything was fiine, I tried to go back out a couple hours later, and I got a "ENG REDUCED POWER" message. I tried to turn it off and restart the car maybe that would fix it... nope. The car still ran so I tried to go around the corner, the first time i stopped at a stop sign I had to restart the car. Then the message didn't appear anymore. I continued to a gas station, got the same message when i got back in the car, and called for service. If anyone has any clue how this happens or how to fix it please let me know. :confuse:
  • drew36drew36 Posts: 1
    I've had a 2005 Express 3500 for awhile now and about 1 year ago I popped a deer on the way to work. This took out the left front quarter along with all the electronics in that area, this was the first I saw of theses lights but a module mounted on that side was busted. Got the van fixed and no problem for 15-20,000 miles. The above mentioned lights came on and all the symptoms as stated from everyone are exactly the same . Shut the engine off and restart works for now. This has happened twice since the wreck on smooth roads with no rain or harsh conditions. One dealer charged to "reprogram" the computer and then told me they would start by replacing the in tank fuel filter, 500+ bucks.I think I will start by checking the engine grounds and the mounting of the fuse box which is oddly enough on the left side under the hood where the deer left his mark. It sounds like these people have a good lead on this problem and several solutions . If you have this same trouble please go to the first post and read all entries ,you'll most likely find your answer.
  • chucka4chucka4 Posts: 1
    2001 Yukon V8 reduced engine power error

    SPOT ON WITH THE HARNESS!!!!!!! My wife called today with the "reduced engine power" alarm. She restarted it and got it home. I found this website and this post. Took note and went to the connector. moved it around an got the same error. went and looked......YELLOW WIRE WAS BROKE!!!. Now, it looks to be about a 8 strand wire which was bent at the connection. I think that they should have used wire with more strand and made it longer to reduce the "KINK". I soldered a long piece in with more strands. Problem fixed.

    THANK YOU GUYS!!!!!!!!!!!!!!!!!!!!!!
  • I have an issue with my truck, the check engine came on along with the reduced engine power warning light? Any ideas what to look for?
  • Does anyone have a photo of what a throttle actuator control (TAC) module is on a 2003 GMC SIERRA 2500HD
  • Help from a start "traction active" displays on dash and you can hear down by the gas pedle inside slipping grinding noise ? and no power not a good thing when your in an intersection ,if I let off the gas and hit it again it takes off , or I have pushed the button on the dash "stability system disabled " and leave it off . is this anything to do with the brown with white stripe plug in under the hood .thanls
  • I also encountered this REDUCED ENGINE POWER on my 03 YUKON XL. I pulled over. Turned the engine off.Waited a few minutes, then turned it on again and turned it off twice. On the third try, the idling went back to smooth and no more REDUCED ENGINE POWER message.This only started when my battery was dying. After replacing the battery with the engine running, the AC don't seem to blow cold air anymore. I dont even hear the AC compressor kick in. You might be wondering why I had the engine running while replacing the battery because I thought I would need a code to unlock my stereo lock.Please help
  • skewterskewter Posts: 2
    OK I have read most of the posts on this and I did a couple of things suggested like the grounding wire, and the wires on top-just jiggled em. It seem to work but I am still having some issues with it starting. The latest is; when turning the vehicle on, it kicks over slow, like it has a low battery, or low charge. The clock will not keep its time so whenever you turn the vehicle off and then start it again, it always goes to 12:00. Could this mean I need a new battery? and why would the reduced engine power lignt come on ever so often? just need some help - dealers are ripoffs and I do not have a mechanic I can trust or the $. thanks in advance
  • bunchz71bunchz71 Posts: 10
    Maybe to me sounds like you have an alternator going out. If the battery is weak, and not fully charged, your ignition system may not get getting the full voltage that is recquired to function properly. Any warning lights on the dash on, other than Reduced Engine Power ?
  • skewterskewter Posts: 2
    Well - I changed the battery and things are back to normal so far- i checked the alternator and it was running great. the battery was dead dead dead. I hope that was the problem, knock on wood. I appreciate all your responses and if i run into any more issues- i will be back on this board - you guys are great! thanks-
  • yukon03yukon03 Posts: 7
    I am just now experiencing this issue as well and I do not think it is my battery or my alternator. Where did you purchase this harness connector?
  • yukon03yukon03 Posts: 7
    Greetings! How did you check the alternator? Did you remove it from the vehicle or check it while it was running? I checked my battery with a voltage meter while it was off (12.3v) and when it was on (14.3). The battery is 29 months old and is a Duralast from Auto Zone! Still have the warranty receipt and was getting ready to head up there and get it replaced until I checked the voltages. Would the harness cause the false/positive voltage check! I am grasping for answers to get this fixed the first time as we are going camping next week and I use my Yuk to pull or pop up camper and I am a little stressed right now!! Any assistance will be greatly appreciated!
  • yukon03yukon03 Posts: 7
    Can anyone tell me where the ground wires are on my 2003 Yukon!! I have read almost every post on this site regarding the Reduced Engine Power situation and I have come to the conclusion by troubleshooting my Yukon and just watching the alternator gauge meter fluctuate that this might fix my problem as well!! The battery and the alternator are fine on my vehicle. If someone could please send me a pic of the ground wire location and that computer/battery harness wire everyone is referring to I would greatly appreciate it!!! My Yuk has been sitting in the driveway for two weeks now because I am afraid to drive it in fear of getting stuck or involved in an accident!! Going camping next week with the pop camper and need to have this problem resolved by then!!Thanks for all of your support, this forum rocks!!!!!!
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