DBW throttle body trouble - The 1947 - Present Chevrolet & GMC Truck Message Board Network

dropd80s · 07-13-2011, 09:36 AM

Having an issue with the DBW TB off an 05 LQ4. With the key on and pedal pressed to the floor, the throttle blade only opens ~50%. We pulled the TB off and pugged into another truck and it opened all the way, so the TB itself should be fine. Any suggestions as to where we should start looking? Pin out and test at the harness? Pedal assembly?

ls1nova71 · 07-13-2011, 10:31 AM

Need a little more info. What year of TAC and pedal are you using? Is it out of the same truck the engine came out of? What year PCM? The TAC and pedal have to match with the tune in the PCM, if you have the '05 PCM then your TAC should have a part number 12590008 (IIRC) and the pedal should be the all plastic type.

Shon · 07-13-2011, 10:44 AM

probably in the tuning of the set up. there are tables in there to only allow the ETC to open certain amounts based on several parameters. It would be better to start the truck and watch the blade but it has to be in Speed Density to do that.
It all can be made to work it just takes the right tune.

dropd80s · 07-13-2011, 05:28 PM

This is in an 05 gmc that origionally had a 4.8. Now has a built LQ4 and PT88 turbo set up. I know the pedal has not been swapped, not sure on PCM and TAC. Will find out more details and get back.

BR3W CITY · 07-13-2011, 09:21 PM

x2 on checking out that the tac, pcm and pedal match together. I had a problem with mine (not the same issue) and getting compatible components solved it right away!

Jim_PA · 07-13-2011, 11:36 PM

The PCM in your truck is likely coded for an EAP (Electronic adjustable pedal) setup. To the best of my knowldege, nobody has unlocked the code for changing this feature.

EAP pedals have about half the total overall pedal travel as those that are fixed.

Been there, done that.... either get yourself an EAP gas pedal and modify it to fit, or find another PCM.

My pedal is the opposite.... at 50% pedal travel, the butterfly is wide open. My solution was to put a new pedal stop in place, or the computer would go into limp mode if I held the pedal beyond the point where the computer was expecting WOT to be.

There is no difference in Accelerator pedal position sensors, there is no difference in tac modules, so it has to be a difference in expected pedal range of motion buried in the PCM somewhere.

A total mismatch in parts would result in a malfunctionig (or non-functional) gas pedal.

dropd80s · 07-14-2011, 10:04 AM

The pedal, PCM, and TAC all match. We are thinking something has put the truck in limp mode causing the reduction in throttle blade movement. The trucks display read "reduced engine power". Didn't get to mess with it yesterday, maybe this afternoon.

Thanks for all your help.

dropd80s · 07-16-2011, 09:34 AM

Correction, PCM had been tuned as an 06, swapped back to an 05 and all is well. Finally back to getting the tune it self dialed in.

07-13-2011, 09:36 AM	#1
dropd80s Registered User Join Date: Mar 2003 Location: wichita falls tx Posts: 429	DBW throttle body trouble Having an issue with the DBW TB off an 05 LQ4. With the key on and pedal pressed to the floor, the throttle blade only opens ~50%. We pulled the TB off and pugged into another truck and it opened all the way, so the TB itself should be fine. Any suggestions as to where we should start looking? Pin out and test at the harness? Pedal assembly? __________________ "I'm Dirk Diggler enough to own and operate a vehicle of this caliber" -veinbar Dropped and LS Swapped SWB 87 Build Thread

07-13-2011, 10:31 AM	#2
ls1nova71 Registered User Join Date: Dec 2009 Location: Independence Mo Posts: 4,119	Re: DBW throttle body trouble Need a little more info. What year of TAC and pedal are you using? Is it out of the same truck the engine came out of? What year PCM? The TAC and pedal have to match with the tune in the PCM, if you have the '05 PCM then your TAC should have a part number 12590008 (IIRC) and the pedal should be the all plastic type.

07-13-2011, 10:44 AM	#3
Shon Registered User Join Date: Sep 2005 Location: sc Posts: 1,203	Re: DBW throttle body trouble probably in the tuning of the set up. there are tables in there to only allow the ETC to open certain amounts based on several parameters. It would be better to start the truck and watch the blade but it has to be in Speed Density to do that. It all can be made to work it just takes the right tune. __________________ 71 Cheyenne C10 LWB cam'd 6.0/T56 Swap

07-13-2011, 05:28 PM	#4
dropd80s Registered User Join Date: Mar 2003 Location: wichita falls tx Posts: 429	Re: DBW throttle body trouble This is in an 05 gmc that origionally had a 4.8. Now has a built LQ4 and PT88 turbo set up. I know the pedal has not been swapped, not sure on PCM and TAC. Will find out more details and get back. __________________ "I'm Dirk Diggler enough to own and operate a vehicle of this caliber" -veinbar Dropped and LS Swapped SWB 87 Build Thread

07-13-2011, 09:21 PM	#5
BR3W CITY meowMEOWmeowMEOW Join Date: Sep 2009 Location: MKE WI Posts: 7,128	Re: DBW throttle body trouble x2 on checking out that the tac, pcm and pedal match together. I had a problem with mine (not the same issue) and getting compatible components solved it right away! __________________ *'66 Short Step / SD Tuned / Big Cam LQ4 / Backhalfed /Built 4l80e / #REBUILDEVERYTHING* MY BUILD THE H8RDCPTR //\\ MY YOUTUBE CHANNEL REV J HD

07-13-2011, 11:36 PM	#6
Jim_PA Registered User Join Date: May 2005 Location: PA Posts: 2,696	Re: DBW throttle body trouble The PCM in your truck is likely coded for an EAP (Electronic adjustable pedal) setup. To the best of my knowldege, nobody has unlocked the code for changing this feature. EAP pedals have about half the total overall pedal travel as those that are fixed. Been there, done that.... either get yourself an EAP gas pedal and modify it to fit, or find another PCM. My pedal is the opposite.... at 50% pedal travel, the butterfly is wide open. My solution was to put a new pedal stop in place, or the computer would go into limp mode if I held the pedal beyond the point where the computer was expecting WOT to be. There is no difference in Accelerator pedal position sensors, there is no difference in tac modules, so it has to be a difference in expected pedal range of motion buried in the PCM somewhere. A total mismatch in parts would result in a malfunctionig (or non-functional) gas pedal.

07-14-2011, 10:04 AM	#7
dropd80s Registered User Join Date: Mar 2003 Location: wichita falls tx Posts: 429	Re: DBW throttle body trouble The pedal, PCM, and TAC all match. We are thinking something has put the truck in limp mode causing the reduction in throttle blade movement. The trucks display read "reduced engine power". Didn't get to mess with it yesterday, maybe this afternoon. Thanks for all your help. __________________ "I'm Dirk Diggler enough to own and operate a vehicle of this caliber" -veinbar Dropped and LS Swapped SWB 87 Build Thread

07-16-2011, 09:34 AM	#8
dropd80s Registered User Join Date: Mar 2003 Location: wichita falls tx Posts: 429	Re: DBW throttle body trouble Correction, PCM had been tuned as an 06, swapped back to an 05 and all is well. Finally back to getting the tune it self dialed in. __________________ "I'm Dirk Diggler enough to own and operate a vehicle of this caliber" -veinbar Dropped and LS Swapped SWB 87 Build Thread

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