Mismatched accel pedal & TAC
 

Tuesday night was the initial startup of the 68's new LS heart. It fired at cranking, then would die immediately when you released the key. I'm getting a P1518 code, communication problem between TAC and PCM.

After poking around the interwebs more, it looks like I have a 2006+ pedal and cable (6-wire rather than 10 for 2003-05)

1. Am I right in assuming that if the PCM isn't getting a signal from the TAC because the TAC isn't getting a signal from the pedal, I'd see P1518?
2. Does the older TAC have to see the APP 2, sensor 3 signal? i.e Can I just move the six newer APP wires to the corresponding cavities and run the older TAC with more empty spots?

The real question is whether it's better to buy another pedal and a 10-wire cable or can the 6-wire drive the older TAC?

Thanks for your input.

Re: Mismatched accel pedal & TAC
 

If it dies when you let off the key, it sounds like you're losing your ignition power in the run position. Or, its a coincidence and its happing because the VATS hasn't been programmed out? As for the pedal and TAC, you didn't say what year your PCM/harness/engine is, but you need the matching parts, you wont be able to repin it and get it to work. So you say you have a 2006 pedal, is it all plastic?

Re: Mismatched accel pedal & TAC
 

The PCM went to Brendan from LT1swap - VATS removal was on my request list.
I also built his relay/fuse block - need to confirm that I have power to the coils in run position. Power for that comes from: the battery for 12V and Ign Unfused on the fuse block for the keyed 12V.

I'm iffy on where off/run/crank for the PCM (blue 75) should come from. It's on a battery hot wire right now.

The scan tool says the PCM is 2003. I didn't pull anything myself, so I don't know exact years for the pieces. The accel pedal is all plastic and has the plug oriented vertically at the upper left. It looked to me like a 2003 pedal had a larger plug at the top center.

Re: Mismatched accel pedal & TAC
 

You want to power the ignition relay, the one that powers up all the ignition (pink) wires in the harness, off of the wire that originally went to the coil, or if you had an HEI, the wire that went to that. The pink Pin 75 wire can be powered off the relay too along with all the others. Brendan has it as "off, run and crank", but its supposed to be "Accessory, run and crank", but you don't need to tie it to the accessory wiring. If your PCM is an 03, then it would be safest, and easiest to get an 03 TAC and pedal with the jumper harness. You need the metal pedal.

Re: Mismatched accel pedal & TAC
 

Thanks for checking back, Nova. There's definitely power to coil/inj/MAF/O2 and to blue 75 on the PCM with the key "on". LKQ is to get me an 03 pedal & TAC harness tomorrow. We'll see how much that cures.

Re: Mismatched accel pedal & TAC
 

I have parts from LKQ, but I'm not convinced they're right. I asked for an '03 Silverado piece.

This pedal has the steel base and the larger plug, but it's only 6 wires. I'm expecting 9 between the pedal and the TAC module. More telling is the pull cable that's built into the pedal arm - this makes me think I still don't have the right pedal. I have yet to find a part number.

Re: Mismatched accel pedal & TAC
 

If it's only 6 wires then its newer, like about an "05 or so. Plus, that is an adjustment pedal. They can be made to work, if you cut the top off and weld your old pedal to it.

Re: Mismatched accel pedal & TAC
 

This is the pedal from my 2003....plug is like yours but pedal assembly is different...

Re: Mismatched accel pedal & TAC
 

Mongo's pedal is the same one I have in my '66 (from an 03.5 van), the other pedal looks like the adjustable/convenience pedals from my 05 Yukon.

Re: Mismatched accel pedal & TAC
 

mogos pic is the same i have from my 2004 pedal

Re: Mismatched accel pedal & TAC
 

Thanks guys - I got the 03 pedal (and TAC module and harness) that looks like everyone else's. That got the truck running long enough to identify a fuel leak. Yes, that is a fire in the tiny pic below. I didn't see too much damage - will check closer once I've calmed down some.

Re: Mismatched accel pedal & TAC
 

holy crap!!!!...that couldve been bad....I don't think a camera would've been the 1st thing I grabbed

Re: Mismatched accel pedal & TAC
 

The young'un was recording the truck's big day - the pic above is one of the last frames that he shot. He did a good job clearing the driveway in case it had to exit the garage.

Re: Mismatched accel pedal & TAC
 

Two words for you: FIRE EXTINGUISHER

Re: Mismatched accel pedal & TAC
 

Yep. Going shopping today to replace the empty. First time I've used one in 30+ years in the garage.

Re: Mismatched accel pedal & TAC
 

Success! In addition to everything being mismatched, I didn't have 12V into the TAC-PCM harness. Thanks guys.

Re: Mismatched accel pedal & TAC
 

hmm ....
I have a 2005 pedal ...... 9 pin ....... going to a 2007 TAC module.

I was just going to buy this ........ but now .......

https://www.ebay.com/itm/2003-2005-V....c100005.m1851