HELP!!!

[michaelgoolsbyinf]

I am at a complete loss. My 2003 chevy tahoe, 5.3 vin t-LM7 keeps going into limp mode. It started, and maybe once a month it would go into limp mode. Error code said throttle body. Ok new Hitachi Throttle Body and wire harness. It was good for another month, limp mode again, I replaced the pedal assy, did not solve anything, replaced the throttle pcm with a new one, nothing, it keeps going into limp mode. Im I keep my foot on the pedal it good, but as soon as I take my foot off, it will go into limp mode. Today I have anew problem also, I parked, came back 20 minutes later, and everything on my cluster now dont work. HELP!!!! I am at a complete loss.

 

[B-train]

Power and grounds is where I'd look. Especially if you live in a salt state. Corrosion does weird things

 

[OR VietVet]

What @B-train said. Sounds like a ground problem. Having worked, ran shops, in a salt on roads state, I have dealt with corrosion problems and lots of times, intermittent problems are connection/grounds related.

 

[drakon543]

definitely possible ground issue or just a separate issue as i believe thats around the year to have terrible clusters. so lets start with the original issue and what bit if experience i have with it. first who did the work you or a shop? during any of all those parts replacements was the battery unhooked for a significant amount of time? if the parts were replaced but the battery was never unhooked and allowed to drain down the remaining electricity in the ecm your liable to still have the same original issue. presuming your have the fly by wire the ecm needs to relearn the home position and swing arc of the tb and the new throttle pedal. leaving the battery unhooked for a significant period of time (30min +) should force the ecm to trigger a relearn. if that was never done your original issue could have just been a lost home position due to an aging tb. ive actually fixed a couple with a similar issue with 0 money spent doing this.

 

[mwilson62000]

Check this thread out.
Thread 'Reduced Engine Power write-up'
https://www.tahoeyukonforum.com/threads/reduced-engine-power-write-up.140235/

 

[michaelgoolsbyinf]

Power and grounds is where I'd look. Especially if you live in a salt state. Corrosion does weird things

I added ground to everything, battery to pcm, pcm to firewall, firewall to side of alternator and computer, fire wall to throttle body. Still getting limp mode just not as bad

 

[michaelgoolsbyinf]

definitely possible ground issue or just a separate issue as i believe thats around the year to have terrible clusters. so lets start with the original issue and what bit if experience i have with it. first who did the work you or a shop? during any of all those parts replacements was the battery unhooked for a significant amount of time? if the parts were replaced but the battery was never unhooked and allowed to drain down the remaining electricity in the ecm your liable to still have the same original issue. presuming your have the fly by wire the ecm needs to relearn the home position and swing arc of the tb and the new throttle pedal. leaving the battery unhooked for a significant period of time (30min +) should force the ecm to trigger a relearn. if that was never done your original issue could have just been a lost home position due to an aging tb. ive actually fixed a couple with a similar issue with 0 money spent doing this.

Yes battery was completely disconnected for 7+ hours. Also solved the cluster issue, it was a wire on the cluster pigtail.

 

[swathdiver]

Yes battery was completely disconnected for 7+ hours. Also solved the cluster issue, it was a wire on the cluster pigtail.

So are you back up and running or still having problems? If not, I suggest subscribing to the troubleshooting guide at AllDataDIY and get after it instead of throwing parts at it.

 

[michaelgoolsbyinf]

Update....
Still having issues with limp mode, I have taken every step I know, throttle body replaced, pcm replaced, pedal replaced, grounds on everything, battery unhooked, during all parts replacement, battery unhooked for 7+ hours, battery unhooked and + and - jumped for 5 hours. One code P1515, I reset, next time its P2135, reset, next time it will be a different code. I am at the point of burn this thing to the ground...LOL

 

[mwilson62000]

Long shot, but on my 03 Tahoe I was having same issue. I started it in my driveway one day and wiggled the throttle body Harness cables, then wiggled the connectors going to the TAC module. (On firewall drivers side) When I wiggled the 16 pin connector, it went into limp mode. I shut it off cleared code, started it and wiggled the connector again and it went into limp mode again. I found that 16 pin harness at lmctruck.com (I think) and soldiered that new harness in place. From that day on for about 2-3 yesar until I sold it, never had it go into limp mode again while driving. I did randomly get limp mode immediately after I started it, but shut it off, wait a few seconds and start it up and would be fine. Only happened maybe once or twice a month. Much bettter than unexpectedly going into limp mode while driving.

 

[tomloans]

This one sounds like the ground behind the engine passenger side. it is likely broken. Tiny little wire bolted to the engine block. Ridiculous design. That little wire will cause all kinds of havoc if not grounded properly. Hard to reach the bolt but can be done with a little finagling. Also clean up the silver ground strap bolted to the drivers side firewall. Take it off and be sure to wire brush both sides of the wire and the bolt at the fire wall. You will see white dust coming off as you do.
.

 

[michaelgoolsbyinf]

Long shot, but on my 03 Tahoe I was having same issue. I started it in my driveway one day and wiggled the throttle body Harness cables, then wiggled the connectors going to the TAC module. (On firewall drivers side) When I wiggled the 16 pin connector, it went into limp mode. I shut it off cleared code, started it and wiggled the connector again and it went into limp mode again. I found that 16 pin harness at lmctruck.com (I think) and soldiered that new harness in place. From that day on for about 2-3 yesar until I sold it, never had it go into limp mode again while driving. I did randomly get limp mode immediately after I started it, but shut it off, wait a few seconds and start it up and would be fine. Only happened maybe once or twice a month. Much bettter than unexpectedly going into limp mode while driving.

I wiggled every connection trying to get it to go limp mode, and can't. Every morning first start it goes immediately to limp mode. Reset, and good for a few hours, then once heat if day it's lime Every 10 minutes

 

[mwilson62000]

Sorry. Did you inspect the ground behind engine on passenger side Like @tomloans mentioned? It’s by the oil sender unit. Very hard to get to unless you pull the intake manifold. See pic. One on the left.

 

[mountie]

Sorry. Did you inspect the ground behind engine on passenger side Like @tomloans mentioned? It’s by the oil sender unit. Very hard to get to unless you pull the intake manifold. See pic. One on the left.View attachment 405953

Are those scary little ground straps the same on my 2005 Yukon 5.3 ??

 

[mwilson62000]

^^Yes.