DBW pedal position correlation with throttle body

[Jim_PA]

My throttle blade is open 100% at half of the gas pedal travel, and extending beyond about 50% of the gas pedal puts me in limp mode.

I have been all over the place trying to come up with a fix for this, and one way is to keep changing OS's until I find one that works with my pedal and TAC, but I really don't want to do that.

Has anyone figured out a way to re-map (or change) the gas pedal correlation with the TAC/PCM?

[Taz]

Hello Jim,

There are some year to year, model to model, compatibility "rules" with APP (gas pedal), TAC (throttle actuator control), TB (throttle body), and PCM OS.

The following information would be helpful:

• what OS are you using
• what APP are you using
• what TAC are you using
• what TB are you using

Once this information is known, the issue may be a simple component mismatch.


Regards,
Taz

[Jim_PA]

Ok, here is what I gathered so far..

OS is 12587603
APP is the fixed metal pedal with a long throw (also tried a 98 corvette pedal with the truck APP sensor and it gives the same result)
TAC is 12573059
TB is the 2003-2005 truck style (the engine and wiring harness is out of a 2004 Silverado 2500)

[Taz]

Hello Jim,

OK ... looks like the TB / TAC / OS are all 2004 vintage truck parts - these should be compatible. Your APP sounds like a 1997 - 2004 Corvette piece - which should work.

Is the PCM from the donor vehicle also, or did you flash the tune into a different PCM ?

When you have a chance, please post your tune - will check for any obvious issues.


Regards,
Taz

[Jim_PA]

Hello Jim,

OK ... looks like the TB / TAC / OS are all 2004 vintage truck parts - these should be compatible. Your APP sounds like a 1997 - 2004 Corvette piece - which should work.

Is the PCM from the donor vehicle also, or did you flash the tune into a different PCM ?

When you have a chance, please post your tune - will check for any obvious issues.


Regards,
Taz

The Corvette pedal sensor did not work. I'm not sure if the sensor was faulty or ... ? I had to swap the sensor off my truck pedal onto the Corvette pedal, but it still gave me 100% WOT at half the pedal travel.

Unfortunately, All I know is that the complete engine/wiring harness came from a 2004 Silverado 2500. The computer, TAC and pedal I have no idea where they came from, but I tried to follow GM PN's to make sure I got things that would work together.


Tune is attached! -- Thanks for looking

[Taz]

Hello Jim,

There are many variables that could be contributing to your current issue - the most probable are the wiring between the APP and the TAC, and the tune file itself.

To recap, you are using a 2004 truck:

• wiring harness
• TAC
• TB
• OS

These should be mutually compatible. I always attempt to minimize variables when troubleshooting a problem. Here is what I would suggest as a course of action:

• full flash the PCM with a 2004 truck CAL & OS - do not move on to a COS until the DBW issue is resolved
• a full flash will write the ETC programming - important if you are using an unknown PCM
• confirm the wiring between the TB and TAC
• confirm the wiring between the TAC and APP
• repin the APP connector as necessary for the specific APP (pedal) being used - truck and Corvette APP pinouts are different

Once the DBW issue is resolved - move onto a COS.

I have attached a PDF file based on 2004 Truck vs Corvette components that should be of assistance.


Regards,
Taz

[Jim_PA]

Oh man. That PDF Is perfect -- THANKS!

I am going to try to use the proper wiring to the corvette APP sensor and check the results. This is the easiest thing I can do at the moment! --

I had the problem before I applied the COS, I've just been dealing with the issue for the last year. I moved the whole LSx setup to a new swap car, and am trying one last time to get this sorted out before adapting the GM pedal to my BMW pedal.

Appreciate it very much! --

[turbo_bu]

Probably a dumb question, but I'll give it a try. As has been repeated many times before, try and keep you PCM / APP / TAC / TB and OS all the same to try and make sure it all works like it should. Now, the question that keeps bugging me, is somewhere in this loop "should" be the key to keeping it all working. Which one of these thing(s) is the key ?????

I have read that on some TB's they have a 0-5 V signal, a 0 - 2.5 V signal, a 5 - 0 V signal, etc... I am not sure if these are accurate or not, but to me, as long as you have the correct wires with the correct signals going into the system (TB, TAC, APP), then that part of the chain should be good. And is maybe not as critical as the rest.

A side thought of this logic comes in that when someone gets a 1/2 throttle input and a 100% WOT TB, it is most likely due to a 0-5 signal going into a 0-2.5 volt input. Don't know, but just a theory.

The next key would be the governor parameters (guessing some form of closed loop PID setup ... maybe only PI??? ... or maybe PD???) Would these only be kept in the TAC, or would they reside in the PCM too? My guess is that this is a little more complicated than just keeping the TB and TAC together .... and making sure the APP has the correct wires connected to the system.

If a person were swapping stuff around, or got dealt a mis-match of parts, would they then have to manually hack the PCM code to put in a different set of DBW PID parameters (guessing with a Tech II to put in a cal for the DBW portion or manually do it in Hex code)? I know these are just random thoughts, but I wanted to throw something out there that might help us to better understand which part ... or are all the parts that critical. Or are there work arounds that have been successfully done.

[Jim_PA]

It's possible. The engine came out of a 2004 2500 silverado, while the computer came from a 2003 3500 GMC Sierra.

I am good for now. I made the pedal stop at 100% throttle opening and when I hooked it into the other pedal, I made sure I had just about a full range of motion so it doesn't seem so sensitive.

[turbo_bu]

Just to confirm, you are using the truck gas pedal (APP) with the truck TAC and TB and it works now? Didn't know if you tried your Corvette APP too (with the wires hooked up correctly ) and got it to work as well.