This is the man issue with Gen III truck setups. How much will #3 charge to “tune” it vs just using the correct pedal?

 

The estimate I got was around $275 via mail order. The problem I have with using a truck pedal is the fact it needs to be cut down to fit under dash which can effect the pedal ratio as well.

 

I'm having the same hair-trigger throttle issue on my 55 I just started driving with a 05, 5.3, LM7. It has already scared me several times. I am using the original truck pedal to the engine, and with the slightest touch it wants to haul ass.
I am having to drive it with my left foot on the brake pedal, to not have surprise acceleration!!!

 

55 rescue dog, did you use the tac module, pedal, and throttle body from the same truck? Just curious, what tac module part number are you using?

I found some info on the 67-72chevytruck forum, but I am not sure if I am allowed to post the link.

 

I used all of it from the original truck. I am using a PSI harness, and their programmed computer.

 

I have the same engine for my 56 but I don't have it installed yet. I hadn't come across this problem in my research. I have the tac module that came with the truck, I'd have to look at the part number. I hadn't figured out what pedal to use with it yet. Is there a recommended one that fits without too much modification?

Sent from my SM-T307U using Tapatalk

 

GM Gen III LS PCM/ECM: Electronic Throttle Equipment Guide

GM Gen III LS PCM/ECM: Electronic Throttle Equipment Guide includes instructional photos, checklists, and step-by-step instructions on upgrading to the GM Gen III LS-Series PCM, ECM, Electronics, and POWERTRAIN CONTROL SYSTEMS

www.lsenginediy.com

I too am very interested since I am installing a 2004 truck engine.
Go to the 2003-2004 truck pedal assembly. Seems to be a difference in how the sensors read pre 2003 and 2003-2004
Unless the programmer eliminated the input from app2 , then I am all wet.
Mike

 

@#%$

 

Just an update for today. I tried a non adjustable/fixed truck gas pedal and no change, same 100% throttle at 50%. I also thought about possible grounding issues with the tac module. I added an extra ground wire to the tac and no change. Also tried a spare tac module with same part number, no change as well.

One thing I forgot to mention was the re-pin for the diesel pedal. I moved a wire from pin E to pin A at the pedal connection.

Thanks again

 

Just an update for today. I tried a non adjustable/fixed truck gas pedal and no change, same 100% throttle at 50%. I also thought about possible grounding issues with the tac module. I added an extra ground wire to the tac and no change. Also tried a spare tac module with same part number, no change as well.

One thing I forgot to mention was the re-pin for the diesel pedal. I moved a wire from pin E to pin A at the pedal connection.

Thanks again

Did you put the wires back to their original position, before trying the truck pedal?

 

I did. Swapped to a spare tac/pedal harness that was unmodified.

 

%$^**

 

Old Buzzard, mine is not a PSI harness, that is 55 Rescue Dogs setup. Mine is a stock truck harness done by me and an ECU tuned by LT1swap.com. Two different harness setups and two different tunes, same issue.

I also posted on a Facebook LS swap group last night and have already had 2 or 3 people say they see the same issue from gen 3 dbw swaps.

I am trying to get this thing beat soon cause this car is due to go on power tour in 3 weeks. Don't want to run my sh!tbox into someone's high-end build. or anybodys pride and joy for that matter.

 

I have an Edge Obd2 display in my 55, and I discovered today that idle the throttle position shows 17%, and at half throttle it is reading 100%. No wonder it's touchy.

 

Per my torque pro app on my phone mine seems to be very similar. My setup is 100% stock 5.3 internally. Mine idles at about 18.2% and is maxed at 99.7% around 50% to 60% pedal travel.

 

I don't have an answer to your problem, but you guys may get more knowledge about DBW throttle body stuff at ls1tech.com or the HPTuners forum.

 

BO185,

Brendan made no adjustments in the tune for the diesel pedal. When I emailed with him he said this is a typical problem with 03-05 gen3 drive by wires. He has no fix for it.

The other tuner I spoke to was almost 100% sure it could be tuned out, but I didn't get the vibe it was "guaranteed". I agree $275 would be cheap if it was a guaranteed fix.

 

I have even seen 03-05 TAC's not work with a part number break among them gm changed vendors and screwed up all kind's of compatibility. If you can get in writing (via email) that tuner says it will work 100% or your money back then I would try it, but then if it doesn't the fight to get money back or it fixed etc.

If it was mine at this point, I would modify the correct truck pedal to fit your needs. But first slave one in and make sure everything works right and tune and harness are pin for it. Nothing wrong with mods to pedal as long as you don't just butcher it.

One thing to note the diesel likes a TB the pedal moves the fueling in the injection pump not a flapper. I have never heard of them being used on an LS (not saying it won't work but oblivious its not for you).


I have a 12588923 TAC that is supposed to sup to a 059 you can have it just pay for shipping to try it. Be like $7-8 bucks what a flat rate box is. That may be one issue potentially. As the Gen III truck DBW is crazy they way they did it.

 

reading my text book about dbw throttle bodies (generic) it says in key off position the flapper is held open by a spring at between 16% and 20%. When running at idle the tb motor has the voltage reversed closing the flapper to close to 0%.

I checked my tb and the key off position the flapper is slightly open. I can push it closed and it springs back to slightly open. ohms testing the tb sensors , pin 1-2 and 9-11 of the 16 pin tac plug (unplugged from tac) I read 4.6k in normal position. 5k ohms when I force the flapper closed and 1.2k at full open. My project is some time away from running so I cannot volt test. There is a warning about the flapper valve can cut off a finger.
Mike

 

The truck sensor body will fit on a Vette pedal frame.

 

BO185,

Thanks for the generous offer of the tac module, but I don't think I will need it.

I worked on the car last night and switched to another tac module I had in the hoard. I forgot I had bought a second module when I bought a truck pedal last summer. The new module is an 059 like my current one, but it seems less sensitive. I put a few miles on the car yesterday and I am already in love with it. Runs great and the drivability (pedal wise) is acceptable at this point.

I may revisit the pedal this winter, but for now I am satisfied. Thanks for all help and the only solution I can offer for anyone experiencing the same issue is to experiment with tac modules.

I am happy with the feel/placement of the diesel pedal so far. I will report back after a few hundred miles on powertour.

 

Since this thread had caught my attention with a similar issue with the hyper sensitive throttle, I thought I should mention what cured mine. The throttle position was going wide open with a light touch on the pedal. Contacted PSI that had programmed the PCM, and they sent a new one with a new tune under an expired warranty at no cost. Now it works perfect, and easy to modulate.

 

Wanted to post a follow up to this to possible help others. I was never able to resolve my issue and switched my car to an earlier pcm and drive by cable a few years back.

Scrolling Facebook a while back i found this post from the owner of lt1swap.com, the place that tuned my pcm. He and I talked about this, but he did not have a fix for the 03-05 tac and mid 1990s GM truck diesel pedal back in 2022. I also talked to a couple of other tuners and they had no idea how to fix. Looks like he now has a work around of flashing in a 2006 operating system. Please see below.

 

Wanted to post a follow up to this to possible help others. I was never able to resolve my issue and switched my car to an earlier pcm and drive by cable a few years back.

Scrolling Facebook a while back i found this post from the owner of lt1swap.com, the place that tuned my pcm. He and I talked about this, but he did not have a fix for the 03-05 tac and mid 1990s GM truck diesel pedal back in 2022. I also talked to a couple of other tuners and they had no idea how to fix. Looks like he now has a work around of flashing in a 2006 operating system. Please see below.

This is one reason I run DBC 100% of time as well as Holley Terminator X. WAY less issues with pedal feel and tuning, as in zero.


Brendan knows his stuff, he had been tuning a long time.

 

@BO185 your recommendation helped push me over the edge to give up on the DBW and switch to DBC. I appreciate the help you offered. Had I made that decision first, I would have avoided the duplicated cost. In the long run, it cost me a new red/blue harness, new 02 sensors, new pcm/ tune, a junkyard throttle body, and lokar style throttle pedal and cable. One advantage is the aftermarket harness is much easier to route and make tidy vs the reworked truck harness. I was able to hide the PCM low in the passenger fender behind the splash shield.

Driving experience is the same between the two systems, DBC and DBW. I will say the driving comfort of the lokar style gas pedal is better than the diesel pedal as the cable pedal offers some adjust-ability of pedal height.

 

I like having a screen for real time data. I actually watch the 3.5'' screen more then anything. They have a 7'' screen that is nice as well. Good with either is you can remove it and stick in glove box for shows.