Drive by wire driving me crazy
Thread Starter
Staging Lane
Joined: Apr 2008
Posts: 93
Likes: 0
From: detroit michigan
Drive by wire driving me crazy 
My throttle body has a mind of it's own, the electronic pedal isn't working at all,the car idles for 7-8 mins tops then shuts off, my personal handheld diagnostic reader is saying no error codes found (allthough the check engine light glows like hot flame) and all the local hot rod shops are treating an LS swap like tabboo unless I have 10 grand to fork over and I am right at the thresh hold of enjoying fuel injection. I don't know what to do, last resort holley carb/edelbrock intake, but I have come so far.http://www.youtube.com/watch?v=IH19cpgyNhw
TECH Regular
Joined: Sep 2007
Posts: 443
Likes: 3
From: Kansas City, MO
What is your pcm, Throtle body, tac module, gas pedal, harness setup? MAF or speed density? How was the pcm tuned for your combo? Make sure your power and grounds are good to the tac module.
Thread Starter
Staging Lane
Joined: Apr 2008
Posts: 93
Likes: 0
From: detroit michigan
PCM/ tac Module/Pedal everything came from the same donor truck 2007 silverado 1500hd 2wd. Speartech did the harness rework/tune. I will double check for the 80th time the connections. Thanks for the response sir, really appreciate it.
Can't you start basic and ohm out the pedal as it moves? Power everything down, hook an ohm meter to the pedal output and see if the measured resistance changes as you move it. If that is good, power everything back up and measure the voltage coming out of the same taps.
you can then work your way along the lines just like testing a bad tail light.
then do the same for the signal from the PCM to the throttle motor.
You might get lucky and find something hooked up wrong. Having no codes and a lit MIL light might suggest that.
you can then work your way along the lines just like testing a bad tail light.
then do the same for the signal from the PCM to the throttle motor.
You might get lucky and find something hooked up wrong. Having no codes and a lit MIL light might suggest that.
TECH Resident
Joined: Apr 2008
Posts: 828
Likes: 12
From: Right here, right now!
John Spears has an excellent reputation for post sale support. Have you given him a call?
Does the throttle body blade respond to pedal movement with key on but engine not running?
It sounds like it is going into limp mode immediately but it is important to see whether the throttle blade moves a little before it goes into limp or does not move at all.
Does the throttle body blade respond to pedal movement with key on but engine not running?
It sounds like it is going into limp mode immediately but it is important to see whether the throttle blade moves a little before it goes into limp or does not move at all.
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With the key in the "run" position, can you step on the gas pedal and do you hear the throttle body "sweep". It sounds like gears grinding, have someone watch it. If it doesn't than you are not communicating with the "tac" module. I just went through a ton of this on a motor swap for a customer. I think I got pretty damn good at! LOL! What year "operating system" did Speartech put on the PCM?
I had a problem with a Speartech harness rewire. People are human and make mistakes. We figured out on another swap that Speartech loaded the wrong OS and year model for the harness that we were using. Double check some things but don't give up!!
There is also a technical bulletin that I found online and verified with my buddy at GM that the throttle body wires will become broken inside the insulation about 3-4" back from the throttle body plug. You have to pull on the wire and see if the insulation turns white to verify breakage. If you need any more help let me know.
I had a problem with a Speartech harness rewire. People are human and make mistakes. We figured out on another swap that Speartech loaded the wrong OS and year model for the harness that we were using. Double check some things but don't give up!!
There is also a technical bulletin that I found online and verified with my buddy at GM that the throttle body wires will become broken inside the insulation about 3-4" back from the throttle body plug. You have to pull on the wire and see if the insulation turns white to verify breakage. If you need any more help let me know.
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Verdad Gallardo Thread Starter
Staging Lane
Joined: Apr 2008
Posts: 93
Likes: 0
From: detroit michigan
John Spears has an excellent reputation for post sale support. Have you given him a call?
Does the throttle body blade respond to pedal movement with key on but engine not running?
It sounds like it is going into limp mode immediately but it is important to see whether the throttle blade moves a little before it goes into limp or does not move at all.
Does the throttle body blade respond to pedal movement with key on but engine not running?
It sounds like it is going into limp mode immediately but it is important to see whether the throttle blade moves a little before it goes into limp or does not move at all.
Thread Starter
Staging Lane
Joined: Apr 2008
Posts: 93
Likes: 0
From: detroit michigan
With the key in the "run" position, can you step on the gas pedal and do you hear the throttle body "sweep". It sounds like gears grinding, have someone watch it. If it doesn't than you are not communicating with the "tac" module. I just went through a ton of this on a motor swap for a customer. I think I got pretty damn good at! LOL! What year "operating system" did Speartech put on the PCM?
I had a problem with a Speartech harness rewire. People are human and make mistakes. We figured out on another swap that Speartech loaded the wrong OS and year model for the harness that we were using. Double check some things but don't give up!!
There is also a technical bulletin that I found online and verified with my buddy at GM that the throttle body wires will become broken inside the insulation about 3-4" back from the throttle body plug. You have to pull on the wire and see if the insulation turns white to verify breakage. If you need any more help let me know.
I had a problem with a Speartech harness rewire. People are human and make mistakes. We figured out on another swap that Speartech loaded the wrong OS and year model for the harness that we were using. Double check some things but don't give up!!
There is also a technical bulletin that I found online and verified with my buddy at GM that the throttle body wires will become broken inside the insulation about 3-4" back from the throttle body plug. You have to pull on the wire and see if the insulation turns white to verify breakage. If you need any more help let me know.
On The Tree
Joined: Jun 2009
Posts: 194
Likes: 0
From: colorado Springs
Subscribed....cause ain't doin' **** either.
Continuity through the motor and TPS1 & 2 When I disconnect the peddle harness at the TAC the RPMS jump. No dash yet so MIL stsatus is unknown. Waiting to borrow a scanner sometime today.
Very frustrated!!!
Continuity through the motor and TPS1 & 2 When I disconnect the peddle harness at the TAC the RPMS jump. No dash yet so MIL stsatus is unknown. Waiting to borrow a scanner sometime today.
Very frustrated!!!
I had an issue with my Drive By Wire. The pedal wouldn't do anything. When i turned the key to the ON Position i could hear the throttle body trying to do something(like a loud clicking), but pedal would not work at all.
My problem was the throttle body was "Stuck". For some reason the blade was slightly digging into the outside of the housing and causing it to stick. If the blade doesn't go where the computer expects it to then it just didn't work at all (like it shut off the system for safety).
First to get it to work I would have my Dad hold the Blade open while i turned the key on. The computer would then move the blade a few times and i had control with pedal. But as soon as the blade got stuck it stopped working again.
I bought a ported and polished throttle body off of ebay for ~ $100 I think(i had to send mine back as a core also). After installing that i have not had any issue with the drive by wire since.
My problem was the throttle body was "Stuck". For some reason the blade was slightly digging into the outside of the housing and causing it to stick. If the blade doesn't go where the computer expects it to then it just didn't work at all (like it shut off the system for safety).
First to get it to work I would have my Dad hold the Blade open while i turned the key on. The computer would then move the blade a few times and i had control with pedal. But as soon as the blade got stuck it stopped working again.
I bought a ported and polished throttle body off of ebay for ~ $100 I think(i had to send mine back as a core also). After installing that i have not had any issue with the drive by wire since.
Check to see if the computer is communicating with the OBD2 connector by unplugging the gas pedal while the engine is running. You don't have to try to throttle it or anything but just unplug it. Maybe they don't have the correct "pin" from the PCM going to the OBD2 connector. If the check engine lamp is on it should display something on your code reader. It should show a code showing the PCM lost communication with the pedal. Also what pedal and TAC module are you running. Are you sure it didn't accidentally get switched? If you give me the part number on the TAC module I can verify the year model. Also in an 07 model you should have the plastic version of the gas pedal and a small 6 pin connector that goes to the pedal from the TAC module. Don't give up. We will help you through all of this.
Thread Starter
Staging Lane
Joined: Apr 2008
Posts: 93
Likes: 0
From: detroit michigan
Check to see if the computer is communicating with the OBD2 connector by unplugging the gas pedal while the engine is running. You don't have to try to throttle it or anything but just unplug it. Maybe they don't have the correct "pin" from the PCM going to the OBD2 connector. If the check engine lamp is on it should display something on your code reader. It should show a code showing the PCM lost communication with the pedal. Also what pedal and TAC module are you running. Are you sure it didn't accidentally get switched? If you give me the part number on the TAC module I can verify the year model. Also in an 07 model you should have the plastic version of the gas pedal and a small 6 pin connector that goes to the pedal from the TAC module. Don't give up. We will help you through all of this.
Staging Lane
Joined: Mar 2002
Posts: 74
Likes: 3
From: Perry Hall, MD USA
Here is a Diagram of how the Throttle by wire system is connected. Look at the very bottom of the diagram for the Pedal wiring to PCM and Throttle Body wiring to PCM.
Things to check for with a Multimeter (Key In Run):
Check all 5 volt References for proper voltage and grounds/low references.
Things to check for with a Multimeter (Key In Run):
Check all 5 volt References for proper voltage and grounds/low references.
Staging Lane
Joined: Mar 2002
Posts: 74
Likes: 3
From: Perry Hall, MD USA
Have you cleaned the throttle body real good? sounds like its just sticking or getting caught up, there not real high torque motors in them so a little bit of resistance and there not gonna budge.