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03 Chevy 2500hd limp mode-throttle body short issue

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I have an 03 2500hd 6 liter.  I had a fisher minute mount 8.6 v plow installed last year. Truck ran awesome until a few months ago.


went into limp mode one day. Found an abs sensor sheared and tapping control arm which shorted ecu. Codes verified this. Replaced ecu and battery, pulled abs relay. Cleared ECU issue code but now we still have a code saying throttle position sensor, throttle body. I’ll get exact code tomorrow. 

we hooked a scanner up and with help of friend watched throttle position percentage and physically watched throttle body. Seems to be in working order and operating as it should. 

Truck starts and idles no problem, but as soon as you drive it and get going around 25-30 it goes into limp mode, door locks flicker, side mirrors start adjusting themselves. 

Any help is greatly appreciated. Snow’s coming soon and I need this thing up and running.

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7 hours ago, davester said:

What do you mean by that?  You connected a bunch of ground cables to the battery?  Or between random spots on the the truck?  Or both?


And what about power?

We checked all grounds we could easily get to and talked to a friend who’s a mechanic locally. He suggested adding a couple new grounds to ensure we didn’t have a ground strap somewhere causing problems.


we added two new grounds from the engine block to ensure we had enough, didn’t change the situation. 

What do you mean “what about power?”



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5 hours ago, David89GMC said:

I had a similar problem.

Be sure to clean the contacts on the throttle body connector and the gas pedal. Your truck is throttle by wire.

We’ve looked at them and they seem to fine. 

when we hooked my buddies scan tool up and checked the throttle body position it seemed to work as it should. 

meaning, I sat in the truck and pressed the gas pedal and could see how much the TB should be open, and my buddy was physically watching it.


when the scan tool showed me throttle position 99.6% open the throttle body was physically wide open.


is it possible there is still a problem in there, if it appears to be working proper?


and yes my truck is throttle by wire.

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So, we have wiggled all wires and nothing goes haywire until we’re actually driving. We can sit and idle and press the gas/throttle with no issue. As soon as we’re moving and we hit the gas it goes into reduced engine power. We hit about 20% throttle when it went into limp mode. 

throwing code p1518- electronic throttle module to pcm communication.



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we have replaced the pedal assembly and our new battery posts (the old ones didn’t have much thread). 

truck fired up and ran decent for 20 minutes. Driving up and down main road at 60-70. 

Then all of a sudden it went back into limp mode. Limped it home. 

Left truck off, popped hood and could hear whining from throttle body so we disconnected the harness and whining stopped, as well as we heard throttle body close. So the throttle body is actuating without the truck being on. 

We have no dash at all, won’t turn over, doesn’t click or even attempt to start but radio turns on, lights turn on, etc.


We’re stuck and don’t even know where to look at this point. 

we are fixing issues for others to simply pop up. Is it possible we have a short somewhere that’s causing these things to go haywire

Edited by Mainedave207
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