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GMC Yukon Reduced Engine Power message



  • I just wanted to let you know that I had the exact same problem in my 2001 yukon xl. Reduced engine power happened about 6 times in a couple of months. I was taking it to the dealer for a recall and on the way there it happened again.
    Frustrated I told them to look at it and fiqure it out. I searched out the best mechanic and he was knowledgeable and worked on it. Said it was a bad ground , charged me 80 bucks and I was on my way. Problem was 5 miles down the road i got reduced engine power again. Turned around and took it back to them. long story short they had it for a week and said they could not fiqure it out . they wanted to throw parts at it starting with a 400 dollar one. I read your thread and told them to check out the wires at the throttle body, they told me they already did, and refused to look at them again. I went and got the truck and decided to go with your suggestion , took apart the cannon plug and found NO broken wires. Decided to replaced the metal contact pins themselves. cut them off and went to a different dealership to parts and look thru a ton of contact until i found the exact ones. replaced them and soldered them just in case and I HAVENT HAD THE PROBLEM SINCE. Im guessing it was just a bad contact pin, just enough to trip the computer.

    Thanks for the info , your time writing your thread probably saved me hundreds of dollars.

    I have never taken a vehicle in my entire life to a dealership for repair , they are thiefs. Look and ask around for a local repair shop with a good reputation. you will save alot of money, and I am NOT talking about a Firestone or something like that, more of a mom and pa shop

    BTW,,,,,,,,,,,,I am a american airlines aircraft mechanic for the last 20 years
  • bunchz71bunchz71 Posts: 10
    Cool, Glad I could help. I had actually already started replacing stuff on my truck. I replaced the Foot pedal, that has the 2 TPS built in to it. It was $120, and it still did not fix the problem. I dont understand why Chevy didnt just keep the throttle cables lol. I never heard of these problems when the throttle was cable-less. haha. I ended up just replacing the entire pigtail end to fix my truck. The pigtail end and about 18" of wire was $140 @ the chevy dealership. I about freaked when he told me how much it was. But I figured, this will fix my truck and I wont have to worry about this annoying problem. If you do want to replace yours as I did, here is the part number.

    AC Delco

    ACD# PT1572
    GM# 88986255

    Hope this helps.
  • afwafw Posts: 2
    I have continually had the same messages displayed on my 2004 Yukon XL. (Reduced Engine Power/Stability Control Disabled/Service 4 Wheel Drive along with the check engine light.) Yesterday for the first time it would not go over about 20 mph. First time it happened the dealer said it was the battery. It was okay for a few weeks, lights on again, but went out the following day. Then it happened a third time, took it to another shop and now is back in the shop again. I will be getting him the information everyone has posted. Have those who thought they had the problem resolved still doing okay, no more lights & messages? By what I have been reading, many people are having the same problems. How do I report this problem to GM? Would a letter writing campaign to GM help this matter?
    Of course, this problem started about 4000 miles after warranty expired.
  • Hi, After the repairs I mentioned about a year ago (bad ground) I have never had anymore problems. *knock on wood*
    When I contacted GM they really just did not care. This issue shows up in the TSBs but what it comes down to is this: Until it kills someone, they won't do anything. I'd really like to know if this has been the cause of any serious accidents. If GM knows, they aren't talking.
    Best of luck to you. I know how frustrating this problem is and I don't wish it on anyone. :)
  • Since I have replaced the plugin where my broken wire was, I have not had ANY problems. It was obviously my problem. My recommendation to anyone that has this problem very intermittently, is to start the vehicle while it is not in Reduced Engine Power Mode and have someone sit in the vehicle, while you wiggle all the wiring, plugs etc on the throttle body. This is the way I solved my problem. The plug in that i had to replace was not cheap, but its worth it to know that it is not going to go into reduced engine mode while a semi is on my [non-permissible content removed] on the interstate.
  • I want to thank everyone for the fantastic information. I have a 2001 Yukon and have been experiencing reduced power intermittenly on a daily basis. It only happens at startup. I shut it off, wait a few seconds, start it back up and then give it a good rev. 8 out of 10 times that does it. The other two takes another cycle. It runs great until I shut it off again. The idiot light comes on occasionally as well. If I run it pretty hard, it usually shuts off. So far my mechanic has replaced the catalytic converter, computer, and performed a fuel system flush. Luckily it is a "mom and pop" establishment and they have not charged me for the computer, fuel flush, or any of the time they have taken to diagnose it. I'm sure they feel that charging me for a cat which did not correct the problem was enough. I'm going back armed with the information you all have provided on the loose ground wire diagnosis. Hopefully that will do it. I will let you know.
  • I have a 2003 Silverado 2500 HD with a 6.0 liter engine. I recognize that I have a different machine, but I would think that there are similar engine components between the vehicles. I have been experienceing Reduced Engine Power message several times over the past 4 days. Local parts store diagnostic check said Throttle Position Sensor is bad. Sensor is not available at parts stores... only through dealership. Parts dept at dealership said TPS only comes as a complete package with a new Throttle Body Assembly. I purchased it and installed it only to have Reduced Engine Power message displayed again.

    I got truck home (at 15 MPH!) and started to examine wiring harness that plugs into the TPS. On my truck, the yellow wire was worn through and is shorting out. A simple wiring connector was the solution, rather than a $260 part. I encourage anyone to check wiring first.
  • looks like you had the exact same problem as I did. It was even the yellow wire that was broke first. The yellow wire was broken with previous owner, this time with me, it was the wire beside it. I dont fully understand the reason for the breaking of wires there. The only thing that I can figure is that its right by the oil filler cap. Maybe it just gets bumped a lot while adding oil etc. Was your plugin like $120??
  • hey bunchz71

    I just had the problem again!!!@! unbelievebly fustrating.
    are you saying that you replace this connector ACD# PT1572 and the wiring to fix the problem???? It was not the brown or yellow wire on the other side??

    I am ready to dump this thing.

    Btw did the wiring come with this connector or is this the price for just the connector??

  • Hey,

    This is what I replaced. Click on the link below and see the plug-in. The connector comes with about 15" or so of "ALL WHITE WIRES". You need to replace one at a time so you do no get them crossed. It comes with 8 wire conectors also. I am not saying that your problem was the same as mine, but its possible. The main reason I went ahead and changed out the whole plug was because the wire was broke off about 1-1/16 from where the wire went into the connector and it made it hard to get a good solder job on the broken wire. I would recommed again wiggling wires with the engine running and have someone sit in the vehicle and let you know when it goes into Reduced Engine Mode. Its best to do it this was that way you know which wires you moved to create the error. Let me know if you need more help. I ll help if I can.
  • 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
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