At about 1/2 of the pedal's mechanical motion, the butterfly on the TB is wide open.

Putting the pedal to the floor does nothing else, but if you're driving and floor it and hold it too long, the PCM goes into limp mode.

Which part needs fixed?

PCM is an '03 GMC 2500 pickup

Motor is an '04 Chevy silverado 2500 pickup

The pedal and TAC were ordered for a 2004 silverado 2500, but I have no idea what I actually got.

I hooked up an '04 silverado PCM, and the pedal is behaving the same way.

 

When it limps, the TB shuts and is non-responsive to the peddle, right? You have the wrong TAC for your PCM. I don't know the correct one, but if that is your symptoms, then that's whats wrong with it. Also I found out that the peddle travel doesn't need to go all the way down to get 100% TB opening when I did the conversion on my dads 72 Chevy. I just adjusted the peddle height (heated and bent the peddle with a torch) in the truck till I got 100% opening just before the peddle was on the floor.

 

Yes, TB shuts, but idles high, and rough! Scared the sh*t out of me. I thought I sent a rod through the block.

I guess a start is to lookup a TAC for an '03 GMC 2500, and see if I can match numbers off the TAC that I have now.

After realizing the problem, it makes sense, because my pedal is currently VERY sensitive, just easing into the throttle is more like giving it half throttle.

 

Ok, so I have a 12573059 TAC module in it now

Book is showing I need a 12588923 --- but other places on the net are advertising 12573059 and 12588923 as being interchangable. I'm hoping they are just wrong???

With any luck my 04 Yukon will have the 12588923 and I can swap them out and see the results before spending any $.

 

Ok, my 04 GMC Yukon has the same 12573059 TAC, so no luck there.

Do you think I might just have a faulty pedal position sensor?

 

I pulled the pedal out of the truck, and took it over to my bone-stock '04 yukon. This pedal is doing the same thing on it, where at half the pedal travel, the butterfly is fully open.

I ordered a brand new pedal position sensor for an '04 GMC yukon, since it appears that whatever is in my Yukon will work in my swap. I'll know Monday if it fixes the problem...

 

so having 200% throttle don't make you go faster?

 

Actually, it does make me go faster, since 1/2 throttle is actually full throttle.

No wonder rolling into the throttle around corners in second gear makes the rear end kick out

 

have had this problem on other trucks at the dealer. replace the pedal assembley.

 

I put in a brand new sensor, and I'm having the same problem. Do I need a pedal from a different vehicle?