GBCM Delete
08-02-2014, 08:47 AM
#1
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GBCM Delete Could you guys help me out with some GBCM delete info. Ive done some searching and dont feel comfortable that I have found my answer. Im doing a harness conversion for a customer and it has the GBCM wiring. Ive already deleted it and pinned the alternator directly to the ECM. Will it work like that or will I have to flash the ECM with an older OS. Also this may be a dumb question, but if I flash the ECM with an older OS could it cause compatibility issues with the TAC. I wouldn't be worried about this at all if the guy was local, but he's have way across the country and I just want to make sure Ive got everything correct before I ship it. This is the 1st GBCM harness I have ran accross so far.
08-02-2014, 09:44 AM
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http://www.lt1swap.com/2004vortec_pcm.htm (highlighted in green)
There are only 2 wire pinned to pcm to remove GBCM, but the alternator doesn't need to be hooked up to the pcm.
There are only 2 wire pinned to pcm to remove GBCM, but the alternator doesn't need to be hooked up to the pcm.
08-02-2014, 01:48 PM
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I realize that you can make it work without the ECM, but I want it to look and work like a factory system. I dont want to go the resistor route. Ive read 3 different things.
1. Just hook the brown wire to pin 15 on green and it will work but the charge voltage may be a little low.
2. Hook both wires to the ecm on pins 15 and 74 and it will work.
3. Do #2 but reflash the ecm with a 2004 OS.
I am sure #3 will work but, I would like to know if this will affect the TAC compatibility with the ecm. Ive read that mixing ECM's and TAC's could cause some issues. I do not have any experiance with this and wonder if changing the OS may cause the same problems.
I belive that #2 will work because the guy on lt1 swap doesnt mention any required programming. I haven't found a mistake on his website yet, so I put allot of faith in his info.
I figure #1 will work as well, especially since the guy said he was going to use an older alternator.
Im just seeking a 2nd opinion on any of the 3.
1. Just hook the brown wire to pin 15 on green and it will work but the charge voltage may be a little low.
2. Hook both wires to the ecm on pins 15 and 74 and it will work.
3. Do #2 but reflash the ecm with a 2004 OS.
I am sure #3 will work but, I would like to know if this will affect the TAC compatibility with the ecm. Ive read that mixing ECM's and TAC's could cause some issues. I do not have any experiance with this and wonder if changing the OS may cause the same problems.
I belive that #2 will work because the guy on lt1 swap doesnt mention any required programming. I haven't found a mistake on his website yet, so I put allot of faith in his info.
I figure #1 will work as well, especially since the guy said he was going to use an older alternator.
Im just seeking a 2nd opinion on any of the 3.
08-02-2014, 04:36 PM
#4
Alternator You didn't say what years were involved but I just ran across a problem with mine. The engine is an 03 Trailblazer LM4 but I had a later (2007) alternator (DR44) and hooked it up per the pinout. It would not charge other than to "fail" to 13.8 volts. Put a 2003 alternator on and it acts normal. I guess the internals of the alternators are different and not compatible with the OS. As far as DBW problems I have been chasing that for two months. If I were you I would have him send his APP, TAC and throttle body to you. Once you flash the PCM hook everything up and see if it works. Good luck!
08-03-2014, 08:32 AM
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The harness he sent me does not have the connector and he said that he does not have an alternator. I am going to set it up for a 1 wire type. If he gets the correct alternator it should be fine I would think.
08-03-2014, 08:34 AM
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You didn't say what years were involved but I just ran across a problem with mine. The engine is an 03 Trailblazer LM4 but I had a later (2007) alternator (DR44) and hooked it up per the pinout. It would not charge other than to "fail" to 13.8 volts. Put a 2003 alternator on and it acts normal. I guess the internals of the alternators are different and not compatible with the OS. As far as DBW problems I have been chasing that for two months. If I were you I would have him send his APP, TAC and throttle body to you. Once you flash the PCM hook everything up and see if it works. Good luck!
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08-03-2014, 11:33 AM
#8
The answer is both yes and no, but mostly no. If you have incompatiblity problems, sometimes they will work as long as the engine isnt running, but as soon as you start it and go past a certain percentage, it will go into limp mode. At least that is what i have found.
08-03-2014, 02:06 PM
#9
Bench test This is the problem I have been fighting, going to limp above about 40% under power. I also just discovered that if I just turn the key on, but not start the car, and press the pedal it will go to limp and set a code. Have been talking to "experts" that cited going to limp mode without the car running and said it was not a mismatch problem.
The initial question was about non-compatible components and if, on the bench, you can get it to 100% open then there is a much better chance that things are working correctly.
Most of the problems I have read about the throttle body will not act lineal and some will only go to about 50% open. This leads me to think that if the pedal and butterfly act together (0-100%) then there should be no problem.
The initial question was about non-compatible components and if, on the bench, you can get it to 100% open then there is a much better chance that things are working correctly.
Most of the problems I have read about the throttle body will not act lineal and some will only go to about 50% open. This leads me to think that if the pedal and butterfly act together (0-100%) then there should be no problem.