Mismatched accel pedal & TAC - The 1947 - Present Chevrolet & GMC Truck Message Board Network

hounddogs! · 02-14-2019, 01:51 PM

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.

ls1nova71 · 02-14-2019, 03:08 PM

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?

hounddogs! · 02-14-2019, 03:23 PM

Quote:

Originally Posted by ls1nova71

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?

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.

ls1nova71 · 02-14-2019, 06:29 PM

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.

hounddogs! · 02-14-2019, 11:31 PM

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.

hounddogs! · 02-24-2019, 05:33 PM

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.

**mongocanfly** · 02-26-2019, 12:00 AM

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

BR3W CITY · 02-26-2019, 10:01 AM

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.

**truckdude239** · 02-28-2019, 11:03 AM

mogos pic is the same i have from my 2004 pedal

hounddogs! · 03-01-2019, 08:33 PM

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.

**mongocanfly** · 03-01-2019, 08:40 PM

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

hounddogs! · 03-02-2019, 01:03 AM

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.

**Wgesnerjr** · 03-02-2019, 07:10 AM

Two words for you: FIRE EXTINGUISHER

hounddogs! · 03-02-2019, 12:20 PM

Quote:

Originally Posted by Wgesnerjr

Two words for you: FIRE EXTINGUISHER

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

hounddogs! · 03-09-2019, 09:03 PM

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

FAKKY · 03-10-2019, 01:08 PM

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

02-14-2019, 01:51 PM	#1
hounddogs! Restoring it $200 at a time... Join Date: Aug 2008 Location: NE Kansas Posts: 887	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. __________________ Charter member of the 'Put the dimmer switch back on the damn floor where it belongs' Society '68 5.3L-4 speed LWB C20; grandpa bought it for the farm in '71. Now LS 5.3, rather than 327. DD '09 Pilot Weekender '65 Skylark 300-4V-4 speed Wife's '07 Lexus ES350; 117 actuator motors and I can't see the engine. Son's '04 F250 SuperCab 6.0

02-14-2019, 03:08 PM	#2
ls1nova71 Registered User Join Date: Dec 2009 Location: Independence Mo Posts: 4,119	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? __________________ My '72 short bed build. http://www.ls1tech.com/forums/conver...6-0-4l80e.html 5.3 swap into my RUSTY '71 C10 http://ls1tech.com/forums/conversion...71-c-10-a.html

02-14-2019, 06:29 PM	#4
ls1nova71 Registered User Join Date: Dec 2009 Location: Independence Mo Posts: 4,119	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. __________________ My '72 short bed build. http://www.ls1tech.com/forums/conver...6-0-4l80e.html 5.3 swap into my RUSTY '71 C10 http://ls1tech.com/forums/conversion...71-c-10-a.html

02-14-2019, 11:31 PM	#5
hounddogs! Restoring it $200 at a time... Join Date: Aug 2008 Location: NE Kansas Posts: 887	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. __________________ Charter member of the 'Put the dimmer switch back on the damn floor where it belongs' Society '68 5.3L-4 speed LWB C20; grandpa bought it for the farm in '71. Now LS 5.3, rather than 327. DD '09 Pilot Weekender '65 Skylark 300-4V-4 speed Wife's '07 Lexus ES350; 117 actuator motors and I can't see the engine. Son's '04 F250 SuperCab 6.0

02-24-2019, 05:33 PM	#6
hounddogs! Restoring it $200 at a time... Join Date: Aug 2008 Location: NE Kansas Posts: 887	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. Attached Images __________________ Charter member of the 'Put the dimmer switch back on the damn floor where it belongs' Society '68 5.3L-4 speed LWB C20; grandpa bought it for the farm in '71. Now LS 5.3, rather than 327. DD '09 Pilot Weekender '65 Skylark 300-4V-4 speed Wife's '07 Lexus ES350; 117 actuator motors and I can't see the engine. Son's '04 F250 SuperCab 6.0

02-26-2019, 12:00 AM	#7
mongocanfly Post Whore Join Date: May 2015 Location: Alabama Posts: 14,671	Re: Mismatched accel pedal & TAC This is the pedal from my 2003....plug is like yours but pedal assembly is different... Attached Images __________________ Mongo...aka Greg RIP Dad RIP Jesse 1981 C30 LQ9 NV4500..http://67-72chevytrucks.com/vboard/s...d.php?t=753598 Mongos AD- LS3 TR6060...http://67-72chevytrucks.com/vboard/s...34#post8522334 Columbus..the 1957 IH 4x4...http://67-72chevytrucks.com/vboard/s...63#post8082563 2023 Chevy Z71..daily driver

02-26-2019, 10:01 AM	#8
BR3W CITY meowMEOWmeowMEOW Join Date: Sep 2009 Location: MKE WI Posts: 7,128	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. __________________ *'66 Short Step / SD Tuned / Big Cam LQ4 / Backhalfed /Built 4l80e / #REBUILDEVERYTHING* MY BUILD THE H8RDCPTR //\\ MY YOUTUBE CHANNEL REV J HD

02-28-2019, 11:03 AM	#9
truckdude239 Senior Member Join Date: Sep 2005 Location: Lewisville, Nc Posts: 10,237	Re: Mismatched accel pedal & TAC mogos pic is the same i have from my 2004 pedal __________________ David fuller Ase Certified Mechanic Click here to help support our board!! 1971 Chevy c-10 under going a 4.8l LSx swap Build Thread http://67-72chevytrucks.com/vboard/s...d.php?t=421305 2007 Honda Accord my daily 145kmiles 2002 Honda Accord 4 door With 330k(sisters car) 2005 toyota Avalon 228k( brothers car) 2002 Sububran 5.3 245k 2000 Tahoe 5.3l 378 General manager for Marco's Carwash & lube

03-01-2019, 08:33 PM	#10
hounddogs! Restoring it $200 at a time... Join Date: Aug 2008 Location: NE Kansas Posts: 887	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. Attached Images __________________ Charter member of the 'Put the dimmer switch back on the damn floor where it belongs' Society '68 5.3L-4 speed LWB C20; grandpa bought it for the farm in '71. Now LS 5.3, rather than 327. DD '09 Pilot Weekender '65 Skylark 300-4V-4 speed Wife's '07 Lexus ES350; 117 actuator motors and I can't see the engine. Son's '04 F250 SuperCab 6.0

03-01-2019, 08:40 PM	#11
mongocanfly Post Whore Join Date: May 2015 Location: Alabama Posts: 14,671	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 __________________ Mongo...aka Greg RIP Dad RIP Jesse 1981 C30 LQ9 NV4500..http://67-72chevytrucks.com/vboard/s...d.php?t=753598 Mongos AD- LS3 TR6060...http://67-72chevytrucks.com/vboard/s...34#post8522334 Columbus..the 1957 IH 4x4...http://67-72chevytrucks.com/vboard/s...63#post8082563 2023 Chevy Z71..daily driver Last edited by mongocanfly; 03-01-2019 at 09:06 PM.

03-02-2019, 01:03 AM	#12
hounddogs! Restoring it $200 at a time... Join Date: Aug 2008 Location: NE Kansas Posts: 887	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. __________________ Charter member of the 'Put the dimmer switch back on the damn floor where it belongs' Society '68 5.3L-4 speed LWB C20; grandpa bought it for the farm in '71. Now LS 5.3, rather than 327. DD '09 Pilot Weekender '65 Skylark 300-4V-4 speed Wife's '07 Lexus ES350; 117 actuator motors and I can't see the engine. Son's '04 F250 SuperCab 6.0

03-02-2019, 07:10 AM	#13
Wgesnerjr Senior Member Join Date: Jun 2015 Location: Atlanta, GA. Posts: 737	Re: Mismatched accel pedal & TAC Two words for you: FIRE EXTINGUISHER __________________ Jay Gesner Atlanta, GA 1985 C10 Long Bed 4X2 LS 5.3, 4L60E Father/Daughter Project

03-09-2019, 09:03 PM	#15
hounddogs! Restoring it $200 at a time... Join Date: Aug 2008 Location: NE Kansas Posts: 887	Re: Mismatched accel pedal & TAC Success! In addition to everything being mismatched, I didn't have 12V into the TAC-PCM harness. Thanks guys. __________________ Charter member of the 'Put the dimmer switch back on the damn floor where it belongs' Society '68 5.3L-4 speed LWB C20; grandpa bought it for the farm in '71. Now LS 5.3, rather than 327. DD '09 Pilot Weekender '65 Skylark 300-4V-4 speed Wife's '07 Lexus ES350; 117 actuator motors and I can't see the engine. Son's '04 F250 SuperCab 6.0

03-10-2019, 01:08 PM	#16
FAKKY Registered User Join Date: Sep 2016 Location: Redington Beach Posts: 1,317	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 __________________ FAKKY 57 PANEL BUILD

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