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I have a major NO THROTTLE RESPONSE issue along with a REDUCED ENGINE POWER message. I have a new throttle body on it. same size as stock. It powers up when i turn the key on and thats it. Codes P0120, P1125, P2120, P2125 are consistent.
Things i have done to fix this issue.
1. checked all wire connections looking for loose ends or damage. I don't see any wire issues but maybe it's super hidden somewhere?
2. Grounds are all clean and tight. I even created a new ground system from the negative terminal to the TAC module, to the Firewall, down to the front side of the head of the engine, to the PCM. Even the "hard to reach grounds on the back of the 5.3" made new ground out of the problem ground ive heard about and cleaned and checked all the wires. Looks good. I have two black grounds that come of the wire harness in the back of the engine. those are good. The only ground i don't have hooked up is the Firewall ground to hood. I doubt that is causing no response from the throttle body. Please correct me if I'm wrong.
4. New sensor at the gas pedal was installed. still no response. (it has a pedal adjuster attached to the gas pedal, not sure if that could cause any issues?)
5. New TPS pigtail connector installed.
Its a fully rebuilt Tahoe. My tuner came over and noticed I had accidentally switched the coil pack plug-ins on the passenger side, he fixed them and the truck started up great. sounded so good! he reved it a couple of times and it sounded awesome, no issues!THEN it happened, turned off the truck, he grabbed the tune kit plugged in and the throttle stopped responding.
It's got a new battery now and still no fix. I am absolutely frustrated. Spent a year rebuilding the Suspension, power train, and a little on interior just to be stopped from driving cause of a random disconnect..
P1125
P2120
P2125
These are the only codes. Please any help would be great. I want to drive the thing I poured my sweat blood and blood into.
What was the original problem that made you start replacing parts?
Did you replace the throttle body in an attempt to fix the issue, or did the issue start after you replaced it?
If you have a decent scanner, you should be able to look at the voltages at the TB and the TAC module.
It could have a broken wire. I know there's a TSB about it, but replacing the TPS pigtail should have fixed it, if that was the actual problem and the repair was done correctly.
The only problem I had originally was the knock sensors and lost communication with TAC module.
I rebuilt the entire truck just do it and learn. The issue started right after my tuner revved the engine a couple of times, turned it off, then it was gone after we turned it back on.
I have a tech 2 and am not too sure how to do that but I will look it up.
I feel like I soldered the wires well and they have an electrical path. I check all of them.
I will post the codes I had before I completely rebuilt it and I will post the codes I am receiving now. Everything seems fine but it is only throwing throttle codes. Before rebuild. After rebuild.
My 05 Tahoe was giving me similar issues and found that I forgot to tighten the ground up top on passenger side of block after an engine swap. It was difficult to get at with intake manifold bolted on but you had mentioned that all grounds were cleaned and tightened so I guess you've ruled the grounds out.
@01CamaroSSTx
Yea I just fixed all the soldering i did on the grounds. I have two that run from the main harness. I extended one and tigheteen it to the throttle body and the other i put a new ground wire on and tighten back behind the block. I also added a bunch of new grounds from battery lol. I dont want any ground issues
Thanks for the reply
@ghardester Thanks for replying. I have a new MAF sensor and checked the wires when i first installed it but I will fosure check them again and confirm they are good to go. Thanks for the help.
Well... all wires have been properly soldered. Grounds are absolutely perfect. Ohm the wires from the TAC module harness to PCM. Nothing is working per usual. Same codes pop up. When checking the inside of the instrument fuse panel, I noticed the fuse pictured does not light up for me when the vehicle is in the on position. I don't know anyone who has this vehicle or I would test it to see if it lights up. Can anyone confirm that it's suppose to light up when in the on position. Light up like probe it.*apparently when updating to LED its common for the Flasher to go bad. I am going to buy a LED flasher to replace the stock flasher. THIS IS HOPEFULLY MY PROBLEM HAHAH
Forgot to test it when I ran the vehicle last cause it ran like dog **** and died. Does not light up when i probe it when vehicle is in on position. Super clean non rusted grounds. No broken wires anywhere This is where the big ground strap goes. Swapped it for the battery cable for ground.
After unplugging my rear HVAC module. I seem to have gotten rid of the "reduced engine power" message and have full connection to the throttle. I am getting an oscilloscope tomorrow to test by serial bus. Crazy how these modules cause interference like that. I am going to test it like a **** and post a update. Hopefully I can keep the connection.
After unplugging my rear HVAC module. I seem to have gotten rid of the "reduced engine power" message and have full connection to the throttle. I am getting an oscilloscope tomorrow to test by serial bus. Crazy how these modules cause interference like that. I am going to test it like a **** and post a update. Hopefully I can keep the connection.
That sounds like working on any Mopar. It is crazy what a module problems will do to the next work.
Please update on what you find with the scope. So is the rear hvac module bad or did unplugging and plugging back in cause the change?
Well, I tested it with the scope with the hvac plugged back in and everything was responding properly with no reduced engine power.
I think the fix could have been the grounds I fixed and cleaned, upgraded to a LED flasher relay (do this if you upgraded any lights to LED), and I updated all modules with pass thru tool and Acdelco sps2.
I will post another update if that message pops up again. Thanks to everyone and good luck with your projects!
05-20-2024, 05:51 PM
REDUCED ENGINE POWER, no throttle response 
