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07-13-2011, 09:36 AM | #1 |
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Join Date: Mar 2003
Location: wichita falls tx
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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?
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"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 |
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Location: Independence Mo
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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.
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07-13-2011, 10:44 AM | #3 |
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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.
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07-13-2011, 05:28 PM | #4 |
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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.
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"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 |
meowMEOWmeowMEOW
Join Date: Sep 2009
Location: MKE WI
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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!
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07-13-2011, 11:36 PM | #6 |
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Join Date: May 2005
Location: PA
Posts: 2,696
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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 |
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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.
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"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 |
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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.
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"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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