Need urgent help, no throttle control.
06-06-2015, 05:19 PM
#1
Need urgent help, no throttle control. I have been working on a 2003 drive by wire LQ4. I took the stock harness, pcm, tac, and pedal and converted to a stand alone harness. I've been trying to start the engine but it has been unsuccessful.
When everything is plugged in and power is applied like turning a key on, the throttle blade moves, but then is almost like it is locked. You can move the pedal and nothing works. You can unplug the pedal and can move the blade by hand again. I have removed the throttle body, tac and pedal and installed in my 2003 Tahoe and everything works as it should. Just don't work on my stand alone harness. I have checked the wiring for resistance and all the throttle body wiring checks out good, two communication wires to pcm check good. I'm stumped. I took the pcm to a local guy to have him disable vats, rear o2's, and turn on pins for electric fans. The first time he uploaded a corvette file and it wouldn't work so I took it back and he put the truck file back in. Acts the same both ways.
If anybody has any suggestions please help me out.
Thanks,
Eric
When everything is plugged in and power is applied like turning a key on, the throttle blade moves, but then is almost like it is locked. You can move the pedal and nothing works. You can unplug the pedal and can move the blade by hand again. I have removed the throttle body, tac and pedal and installed in my 2003 Tahoe and everything works as it should. Just don't work on my stand alone harness. I have checked the wiring for resistance and all the throttle body wiring checks out good, two communication wires to pcm check good. I'm stumped. I took the pcm to a local guy to have him disable vats, rear o2's, and turn on pins for electric fans. The first time he uploaded a corvette file and it wouldn't work so I took it back and he put the truck file back in. Acts the same both ways.
If anybody has any suggestions please help me out.
Thanks,
Eric
06-06-2015, 07:17 PM
#2
Dbw I can only tell you what happened to me and take it from there. Most (maybe all) tuners put a tune in for an '05 because of all the updates. If this is the case then the '03 TAC and APP will not work and must be upgraded to the '05 stuff. Do a search on this forum for the correct TAC and APP. I have posted the numbers several times. It's not fun but hang in there and you WILL get the right combo.
06-06-2015, 08:50 PM
#3
If you have a local tuner, he should be able to scan the DBW data and see what is happening. There are tons of PID's to show what the pedal and throttle body readings are. Likely the tuner is not using a file compatible with the hardware. Verify you have power at the tacc module too.
06-07-2015, 11:28 AM
#4
Thanks for the suggestions guys.
Here is what I have so far, all wires are good and have power where needed. I pulled the pcm from my 2003 Tahoe and it works on my stand alone harness and pedal works as it should. While hooked to a Snap On Verus scan tool at the shop I work at, looking at TAC data the values show 100% wide open so all is good on that end. When I connect the Yukon pcm that come with my engine, no throttle. No codes are pulled either.
Here are some part #'s
TAC module 12573059 (same as my 2003 Tahoe also)
Yukon PCM
Service # 12576106
Hardware # 12570558
Tahoe PCM
Service # 12582605
Hardware # 12580786
On the 6.0 Yukon pcm, he had changed the file to a corvette but changed it back yesterday to the stock truck file he pulled from it, disabled vats, rear o2's, and turned fan pins on. No control over the throttle. I can install this pcm in my Tahoe and soon as you start it, it goes wide open throttle. With key on, moving pedal will not work throttle body. No codes are set either.
I can put the Tahoe pcm on my 6.0 stand alone harness and have full function over everything, just won't start due to security stuff.
One thing I did notice with the Yukon pcm on my 6.0 is when trying to start it, it was only hitting on #5 cylinder. I have fuel pressure on the rails, spark on all cylinders, power on all injectors also. The plugs didn't seem wet except #5 where it was firing. I'm beginning to think I have a bad pcm or the file is just wrong on it. Looking at the sensor data with this pcm, it does show crank and cam counts, coolant temp, and all like it should be. Just no throttle data.
Here is what I have so far, all wires are good and have power where needed. I pulled the pcm from my 2003 Tahoe and it works on my stand alone harness and pedal works as it should. While hooked to a Snap On Verus scan tool at the shop I work at, looking at TAC data the values show 100% wide open so all is good on that end. When I connect the Yukon pcm that come with my engine, no throttle. No codes are pulled either.
Here are some part #'s
TAC module 12573059 (same as my 2003 Tahoe also)
Yukon PCM
Service # 12576106
Hardware # 12570558
Tahoe PCM
Service # 12582605
Hardware # 12580786
On the 6.0 Yukon pcm, he had changed the file to a corvette but changed it back yesterday to the stock truck file he pulled from it, disabled vats, rear o2's, and turned fan pins on. No control over the throttle. I can install this pcm in my Tahoe and soon as you start it, it goes wide open throttle. With key on, moving pedal will not work throttle body. No codes are set either.
I can put the Tahoe pcm on my 6.0 stand alone harness and have full function over everything, just won't start due to security stuff.
One thing I did notice with the Yukon pcm on my 6.0 is when trying to start it, it was only hitting on #5 cylinder. I have fuel pressure on the rails, spark on all cylinders, power on all injectors also. The plugs didn't seem wet except #5 where it was firing. I'm beginning to think I have a bad pcm or the file is just wrong on it. Looking at the sensor data with this pcm, it does show crank and cam counts, coolant temp, and all like it should be. Just no throttle data.
06-07-2015, 02:11 PM
#6
I could see that, but the throttle body works flawlessly on my Tahoe, as do the TAC and pedal. They just won't work when I hook up the Yukon PCM I had the vats and emissions disabled on. I'm thinking it is a PCM conflict with the tac but all three pieces are from the same Yukon.
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06-07-2015, 02:17 PM
#8
I did, swapped them into my Tahoe and the throttle body locks and with pedal movement there is no blade response. Put the Tahoe PCM on my stand alone harness and the throttle works perfect. The Yukon 6.0 PCM locks both throttle bodies and there is no pedal response on both my Tahoe and the 6.0 stand alone harness.
My tuner said the Yukon 6.0 pcm still has the stock 03 file on it, just a few things disabled.
My tuner said the Yukon 6.0 pcm still has the stock 03 file on it, just a few things disabled.
06-07-2015, 02:50 PM
#10
I have full pedal throttle control with the Tahoe PCM. Just won't start due to security stuff.
My swap 6.0 come with harness, PCM, TAC, and pedal all from same 2003 Yukon XL. I modified the harness to a stand alone with a fuse and relay box from BP Automotive. Had a local tuner disable vats and stuff on the PCM but it don't work. I guess I need to have him change the file again.
My swap 6.0 come with harness, PCM, TAC, and pedal all from same 2003 Yukon XL. I modified the harness to a stand alone with a fuse and relay box from BP Automotive. Had a local tuner disable vats and stuff on the PCM but it don't work. I guess I need to have him change the file again.
06-08-2015, 07:44 AM
#12
I had what sounds like the same issue with my swap and it turned out that the tac motor control wires were reversed on the throttle body. The throttle body would open and close when the key was turned on, but had no pedal control whatsoever. Reversed the Brown and Yellow wires at the throttle body and all was solved. In my case, this had nothing to do with the tune file. It's worth trying.
https://ls1tech.com/forums/conversio...2-dbw-how.html
https://ls1tech.com/forums/conversio...2-dbw-how.html
