A little background first. I have a '68 C10 that I swapped in a 05 5.3L. I'm using an LS6 intake and a TB/pedal/TAC/PCM from an '04. I tuned it with HPtuner to basically remove the VATS and a few other minor changes. I've been driving the truck for over 6 years (occasionally) and have 2000 miles on the swap with no problems.

Last week I was getting the truck all washed up for Hot Rod Power Tour and I went to spray off the engine as there was muddy cat paw prints on top of the engine. Once I finished spraying it off, I pulled it into the shop to dry it off. Then I pulled it onto the lift to remove the wheels to polish them up. When I did this a CEL came on and the truck reved up and was pushing with the brakes on. I got it on the lift and polished up the wheels. Later that night I scanned the computer and got several codes (P2125 and a few others). I checked the wiring to the TB and it all appeared fine.

So the next morning I went and got a new TB, a used TB, a used TAC module. I swapped out this piece and that and there was no difference. I then changed out the pigtail from the TB. I tested it again and no change. The TB was still acting up.

I was out of time at this point and drove it to HRPT (2 miles away from the house) and was able to get there by clearing the codes. Once the show was over I drove home with no issues. I was thinking that if water got in somewhere, it had evaporated and I was hopeful.

Once I got home I let it just idle for a bit, and it set off the codes again. So I went and got a new accelerator pedal position sensor. Plugged it in and no change. I again checked the wiring and can't find anything.

I went on one leg of HRPT in my jeep (rather than my truck ) and yesterday I checked it again....same results. I did notice that as I'm scanning, sometimes if I clear the DTCs, it HPTuner and the ECM will disconnect.

Any suggestions on what to check for? I did check for 5v and grounds at the TB. I do have another ECM, but if I try to use it, I will have to buy more credits in order to get around the VATS.

It's just so weird that I haven't had any problems until I washed the engine, but at this point it should have had plenty of time to dry out.

 

Make a config with the scanner using every possible ETC, TPS and Pedal PIDs you can select from the list. With KOEO scan the vehicle while working the pedal through it's full range looking at everything you are logging and see if something looks out of norm.

 

Water in the tacc module or electronics of the throttle body. Open the tacc and inspect. I have spares if you need either part.

 

I got a new tac module and TB. The tac module is in the cab anyways.

 

I can email you a cfg which i use for testing the dbw systens if you want it.

 

So i did a little testing tonight.

from the wiring harness coming from the TAC module to the accelerator pedal I'm getting 5V on the gray wire (supposed to be low ref), dark green wire (my wiring diagram says not used), Purple wire (low reference), and white/black wire (5V)

I'm getting 0V on the yellow/black wire and tan wire

this is with both TAC modules