Jump to content

Stuck in Reduced Engine Power

ChrisMills

By ChrisMills
in Ask A GM Technician

 Share

Recommended Posts

ChrisMills Enthusiast

ChrisMills

Posted
Posted

2004 GMC Sierra 2500HD 6.0l 4wd auto trans

 

Awhile back the truck went into reduced engine power mode on startup one morning. I turned the key to the off position and removed it. The engine kept running and the dashboard lights flashed.

 

Discovered that i can stall the engine with key in run position by turning on the high beams. The driver side headlight is dim with DRL running.

 

Got trouble code U0107

 

 Normally this would seem pretty straightforward. It's saying that there's a problem with the throttle control system somewhere. The thing is that the issue of the engine not shutting off with the key removed complicates things. It suggests that something else is going on.

 

 I originally posted this question in the wrong section as i'm a newbie here. There's a bit more background in that thread.

 

https://www.gm-trucks.com/forums/topic/226118-stubborn-problem/

 

 Anyway ... been going round and round with this one for awhile now. Have researched the heck out of it and tried all kinds of things but not making any progress. Maybe i'm too close to it and missing the obvious ?

 

 Maybe somebody else has seen this before ?

 

 Any suggestions on what else i might try ?

ChrisMills Enthusiast

ChrisMills

Posted
  • Author
Posted

Ok .. i went to the under hood relay center and pulled all the non-essentials one at a time.

 

 When i removed the HDLP-LOW relay the truck started up and shut off normally. No reduced engine power message and the throttle works just fine.

 

 This is the first sign of progress in months.

riverbanks Senior Enthusiast

riverbanks

Posted
Posted

The fuses for left and right are after the relay,leave relay in,pull fuse one at a time,try to isolate further

ChrisMills Enthusiast

ChrisMills

Posted
  • Author
Posted

Sounds good.

 

Pulling the Lo HDLP-R fuse had no positive effect.

 

Pulling the Lo HDLP-L fuse had a positive effect. The left ( driver side) headlight & dash cluster were knocked out but the truck started and shut down normally. There was throttle response so it's probably safe to assume that the truck wasn't in reduced engine power mode.

ChrisMills Enthusiast

ChrisMills

Posted
  • Author
Posted

Pulled headlight assembly and inspected wiring in that area. No visible damage. Broke two electrical harness connectors and no sign of corrosion.

 

(Side note: Discovered that the power steering cooler has a leak at the top. That area is a bit of an oily mess.)

 

 Pulled bulb: The truck started and shut down normally. Throttle response a bit sluggish but it was there. No power to dash cluster.

 

 Re-installed bulb: Dash cluster out, but the truck appeared to be in reduced power mode. No throttle response and truck shut down abnormally.

ChrisMills Enthusiast

ChrisMills

Posted
  • Author
Posted

River,

 

 Don't want to jump the gun but this seems mostly solved. The problem at hand was that it was stuck in reduced engine power with no solution in sight.

 

 I really appreciate your help. It got my truck restoration project unstuck and moving forward again. Was figuring a 6 - 12 month time frame for the project when i bought the truck last January. ( It's a patient process. )

 

 The very front of the truck needs some work. Was planning on replacing the front bumper & power steering cooler anyway so might as well pull the grill and open the front right up. You know ... give it all a good degreasing, inspect the entire wiring harness for damage, remake all of the ground contacts and so on. ( Whatever it needs to bring it up to spec.)

 

 It's a good bit more work and expense but it's worth it. The work holds if it's done right the first time. I might not have to go back in there for as long as i own the truck.

 

 Again ... many thanks for your help and guidance.

  • 1 year later...
  • 6 months later...
sledbuttrob New Member

sledbuttrob

Posted
Posted

Did you get a response on this?  I have had the same problem for 8 months.  Replaced everything including grounds.  I noticed a month ago I had a dim headlamp.  Pulled the relay and now I have a gas pedal.  How do I fix this?  

 

Anybody?

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share
Go to topic listing

  • Latest Articles

  • Posts

    • Chuck FB
      Fluid Change Questions

      By Chuck FB · Posted

      I know when I was looking around last year to see if someone handled Amsoil gear oil to buy at the retail level which of course means full price. I found an independent shop that works a lot on GM/Duramax pickups and they did not bring in the 75W-85 as they just stuck to the 75W-90 for the front and rear as a standard practice for the HD trucks which makes sense anyway for the higher hp/torque diesel and pulling heavy loads in four wheel drive. I haven't changed my diff oils yet but still plan on using the 75W-85 for the front diff as I highly doubt I will be beating on the truck and figured for my use type the bit thinner oil would be to my benefit for the winter for that slightly less drag. Very different weather here all winter vs northern Washington near the coast, that's for sure. 
    • Chuck FB
      Oil Consumption

      By Chuck FB · Posted

      Ok that confirms the extra quart theme they are still going with which must mean they have noted some initial use more so then some engines and probably the bigger factor in all of this probably isn't the engine so much as its the insane distance or OLM that lulls a lot of the driving public into driving their new vehicle off the lot and not even doing one short interval oil change because the manufacturer doesn't say different and if the dealer follows that logic as well. Selling the rarely needing to be serviced concept seems to go over well with the public that wants to get away with as little as possible for dollars spent on the vehicles maintenance and I bet there are 3.0 engines just like other vehicles out there that never have their oil checked by the owner which goes back to why they probably felt the need to add that extra quart to avoid a costly theme.    Speaking of cutting filters open, it was probably over two years ago now that a youtuber who buys vehicles to do longer term reviews and pulls a fifth wheel through the mountains of Colorado on summer trips and that becomes part of the testing. Anyway he had a GM HD with the 6.6 gas and a Ford 250 with the 7.3 gas at the same time and of no surprise the Ford had more power etc but somewhere along the way in the few thousand miles he put on the truck, he changed the oil and was seeing glitter and cut open the filter and yeah, things were not looking spectacular. The truck about that time or soon after seemed down on power compared to what it had been and then threw some engine code, I expect the cam/lifters were failing and so he brought the truck back to the dealer and made some deal to get out of it as he knew it would sit for months waiting on a new engine as they were so backlogged at the time. He kept the GM for some time after that using it exclusively until he sold it after buying his next vehicle to do a review on. Definitely the filter can tell a story when things are starting to go sideways, but it would be a sickening feeling to cut it open and be faced with an ugly mess like that and be running a magnet through the pleats and the oil on the dirty side of the filter and see all the fines sticking to the magnet.    The dealer may have some ideas based on experience as to where that coolant smell is coming from, I would imagine if they can't find it but its smelling they would put dye in it to they could give it a run cycle and use the black light to see where it pops up, if its a hose connection, water pump, rad or even a head gasket etc. 
    • riddler
      Torsion adjustment

      By riddler · Posted

      Good looking truck, suspensionmaxx looks like a solid option
    • riddler
      Torsion adjustment

      By riddler · Posted

      Thanks for the info, im considering a leveling kit or 4" lift kit.
    • davester
      frustrating P0446 code

      By davester · Posted

      charm.li (website) has the vehicle-specific diagnostic procedure for that code, you can use to find what the cause of it is.

  • GM-Trucks.com Clubs

  • Popular Contributors

×
×
  • Create New...