I’m new here.Sorry this going to be a long post.Back in July I was hauling a 14000lb horse trailer on 95 degree day.I lost power at some point threw my trip.My truck started to shift really hard I couldn’t here my turbo like normal and my exhaust brake didn’t perform as normal.Got the truck home and it didn’t do the normal hiss at idle and change to rumble.I took it to a garage and they said the turbo was bad.Had a Warranty so I got a turbo put on.The garage pulled my cab off to do it.Which I was sketchy about.I got my truck back had the rumble and hiss back again and exhaust brake worked as normal.Still shifted hard hooked to my trailer.About 2.5 weeks later my I get service stabilitrak,traction control and trailer wires.Gauges all flicker doors unlock and lock themselves.unhook battery it go’s away for a day or two.Then truck won’t start.unhook battery hook it back up runs fine for a couple days.Had to get my horse trailer from dealer.get on the highway all the service lights go on door locks locking unlocking gauges flickering acts like it’s going into neutral.H and s tuner says it lost connection.limp it to a garage.Start and runs fine the next day.Had p0700,P0575,p0703,P2510,P0856 codes.They went over some connections from having the cab off and couldn’t figure it out.runs fine for a couple days act up again.took it to dealership this time.They had it a week and a half.Said it ran fine had a couple errors but they couldn’t figure it out by them.Tell me to bring it back when it’s acting up.Wont start again get it running take to the garage that put the turbo on again.They go over Tcm wiring put a speed sensor on it.wont start again tell me to take it to a different dealer.Have it towed there because it won’t start.they call me and ask me why I had it towed there because it starts and runs fine for them.They Had it 3 weeks.said the wiring harness to the Tcm was missing a piece it wasn’t plugged in all the way.said it would start the line under park was missing.the pushed the Tcm connector in all the way.line comes back starts up runs good.They put some zip ties on to hold it together.I picked it up runs fine for two and a half weeks.got on the throttle a little bit set off service traction control and all that bs.ran codes on tuner.got p0703,p0856.next day start it remote fifes up shuts off!Wont start.get home from work starts up service traction control and all that bs is on.H and s tuner says it can’t connect.take it for a ride no power tranny shifts hard.get home shut it off.Get codes p0575 p0703 p0856.Sorry for the lon post!I have been dealing with this for months now.Any advice would be greatly appreciated!Thank you in advance! 2011 lml deleted with h and s tuner
Guidolml
Your problem sounds intermittent, like a wire rubbing or a connector that sometimes opens up a little. Where are you located? Rust/salt belt? Anyone checked/cleaned the ground points? As you've already found out, this will not be an easy problem to solve. Has your TCM ever been replaced? Many 11's have had TCM problems, although your current DTC's would not indicate a TCM problem. It could be a component (door switch, seat motor, etc) taking out the GMLAN system intermittently, and it would take a scope and someone who will obtain and read the eletrical charts for your truck. There are some ground points just above and to the outside of the dash speakers near the firewall that many have found cause a multitude of problems that sound like yours. Look at the one on the drivers side first. The problem could be really simple to find, IF you have the correct person looking for the problem. You need to find someone who specializes in electrical diagnosis, not a diesel mechanic that may be great at replacing damaged or worn out parts. You need someone who will test their diagnosis to be sure they have really found the problem and can duplicate the problem and proposed repair. BEFORE they make the call on what to fix or replace. Many auto electric shops are very good at this. Perhaps you have one nearby??
I live in Erie Pennsylvania so definitely in the salt belt! The mechanic at the dealership said my Tcm says AcDelco on the back do he said it was changed at one time.He also said that once the Tcm has been changed they normally don’t cause anymore problems.I don’t know how true that statement is?I don’t know of any electrical mechanics around?I will have to ask around.Thank you for the help!
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