Keeping the Vortec 5.3L Generator Battery Control Module (GBCM).
12-03-2013, 08:00 PM
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Keeping the Vortec 5.3L Generator Battery Control Module (GBCM). For those wishing to keep and maintain the GBCM PCM programming and GBCM function for your '05 5.3L Vortec (Non-Hybrid) engine application, this may help. It may be applicable to other year and CID models too.
The GBCM was put in place to control the alternator charging behavior to improve engine fuel economy, performance and cut down on wear & tear of the alternator. The fact it is still an OEM feature says a little about the validity of purpose. I've read plenty "How to Delete" posts but none with the basic information about how to "Keep" and connect the GBCU wiring. After a good deal of research through wiring diagrams in AllData, here's what I've learned.
The GBCU Connector has 10 Pins.
Pin's A & C (Red/White) (Circuit 4740) are both positive battery voltage supply wires; 10 amp fused battery feeds to the GBCM.
Pin B (Gray) (Circuit 23) is the Generator Field Duty Cycle Control wire; connects to the OEM alternator plug; one of two wires. This wire is also spliced / tied to the PCM Green connector Pin #75; the Generator Field Duty Cycle Signal. In short, there is no need to alter these connections in the OEM harness.
Pin D (Brown) (Circuit 25) is the Charge Indicator Control wire; connects to the OEM alternator plug; the second of two wires. There is no need to alter this connection in the OEM harness.
Pin E is not used; a cavity.
Pin's F & H (Black/White) (Circuit 451) are both Ground wires; connect to the OEM harness ground Splice Pack and ultimately are grounded to the engine block. There is no need to alter this connection in the OEM harness.
Pin G (Dark Blue) (Circuit 5668) is the "Engine On" signal for the Power Brake Supplemental Brake Assist (SBA) Pump Motor. The SBA unit uses this wire to determine if the engine is running so it can run its initial start-up diagnostic features. For more info on the SBA pump and its operation, Google it. Otherwise this circuit is not needed for the GBCM operation and can be properly stowed or removed if the Supplemental Brake Assist System is not part of your application.
Pin J (Purple) (Circuit 5428) is the Generator Regulator Control wire. Connects to the PCM Green connector Pin #15. There is no need to alter this connection in the OEM harness.
Pin K (Orange/Black) (Circuit 6752) is the Class 2 Serial Data wire. Connects to the main splice pack (SP205) for Pin 2 of the OBD2 Data Link Connector. There are numerous OEM Class 2 Serial Data wires from various vehicle modules that connect to the OBD2 main serial data wire. There are also some that do not; like PCM Blue connector Pin 59.
I hope everyone finds this information helpful.
The GBCM was put in place to control the alternator charging behavior to improve engine fuel economy, performance and cut down on wear & tear of the alternator. The fact it is still an OEM feature says a little about the validity of purpose. I've read plenty "How to Delete" posts but none with the basic information about how to "Keep" and connect the GBCU wiring. After a good deal of research through wiring diagrams in AllData, here's what I've learned.
The GBCU Connector has 10 Pins.
Pin's A & C (Red/White) (Circuit 4740) are both positive battery voltage supply wires; 10 amp fused battery feeds to the GBCM.
Pin B (Gray) (Circuit 23) is the Generator Field Duty Cycle Control wire; connects to the OEM alternator plug; one of two wires. This wire is also spliced / tied to the PCM Green connector Pin #75; the Generator Field Duty Cycle Signal. In short, there is no need to alter these connections in the OEM harness.
Pin D (Brown) (Circuit 25) is the Charge Indicator Control wire; connects to the OEM alternator plug; the second of two wires. There is no need to alter this connection in the OEM harness.
Pin E is not used; a cavity.
Pin's F & H (Black/White) (Circuit 451) are both Ground wires; connect to the OEM harness ground Splice Pack and ultimately are grounded to the engine block. There is no need to alter this connection in the OEM harness.
Pin G (Dark Blue) (Circuit 5668) is the "Engine On" signal for the Power Brake Supplemental Brake Assist (SBA) Pump Motor. The SBA unit uses this wire to determine if the engine is running so it can run its initial start-up diagnostic features. For more info on the SBA pump and its operation, Google it. Otherwise this circuit is not needed for the GBCM operation and can be properly stowed or removed if the Supplemental Brake Assist System is not part of your application.
Pin J (Purple) (Circuit 5428) is the Generator Regulator Control wire. Connects to the PCM Green connector Pin #15. There is no need to alter this connection in the OEM harness.
Pin K (Orange/Black) (Circuit 6752) is the Class 2 Serial Data wire. Connects to the main splice pack (SP205) for Pin 2 of the OBD2 Data Link Connector. There are numerous OEM Class 2 Serial Data wires from various vehicle modules that connect to the OBD2 main serial data wire. There are also some that do not; like PCM Blue connector Pin 59.
I hope everyone finds this information helpful.
Last edited by Fivetears; 12-03-2013 at 08:06 PM.
03-04-2014, 06:00 PM
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thank you FiveTears! this helped me out with the pin out for the 2 wires gray and brown to pin it out to a 411 ls1 set up
brown pins out to R15
gray pins out to R75
hope this also helps someone
brown pins out to R15
gray pins out to R75
hope this also helps someone
02-08-2016, 12:44 PM
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Hey thanks, this helped me with trying to figure out what to do with my GCBM. That blue wire 5668 was making me nervous. The difference between my setup and yours is nothing from the GBCM ever went to the PCM. It seems like a standalone unit almost, minus the 5668 and the 6752, which goes to the ODB according to my diagram. The brown and grey from the alternator go directly into the GCBM module, which sort of makes sense. I was considering deleting this but seeing other people having problems after kept me from doing it. Oh and I forgot, mine is an 07 L33
02-09-2016, 04:49 PM
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One more question Fivetears, it's hard to tell on the diagram: Is cct 4740 switched with ignition? Being red and white kind of puts it into a gray area
02-10-2016, 08:01 AM
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Circuit 4740. This animal begins at the Underhood Fuse Block in a 2005 GMC Sierra. It's part of the Regulated Voltage Control circuitry. It is fed by positive battery voltage (B+). Battery voltage then passes through an RVC (Regulated Voltage Control) 10 amp fuse and splits into two RD/WH 4740 0.5 gage feed wires, leaving the Underhood Fuse Block at pin D5. These two wire are connected to pins A and C of the GBCM.
To answer your question more precisely requires some investigatory work on your part. The 2005 GMC Sierra Underhood Fuse Block also contains the Cigarette Lighter 15 amp fuse. As you may know, some GM vehicles have power to the cigarette lighter at all times and some do not. Can you charge a phone in a 2005 GMC Sierra with the ignition off? If you can answer that question, you'll have the answer to your question.
I say YES. I connected this circuit directly to the battery using an inline 10amp fuse. My setup performs flawlessly. In my opinion, B+ in a GM wire diagram means constant battery voltage. However, since I don't own a 2005 GMC Sierra, I can't verify this proof positive. You'll have to make the final call on your end.
Hope this helps.
To answer your question more precisely requires some investigatory work on your part. The 2005 GMC Sierra Underhood Fuse Block also contains the Cigarette Lighter 15 amp fuse. As you may know, some GM vehicles have power to the cigarette lighter at all times and some do not. Can you charge a phone in a 2005 GMC Sierra with the ignition off? If you can answer that question, you'll have the answer to your question.
I say YES. I connected this circuit directly to the battery using an inline 10amp fuse. My setup performs flawlessly. In my opinion, B+ in a GM wire diagram means constant battery voltage. However, since I don't own a 2005 GMC Sierra, I can't verify this proof positive. You'll have to make the final call on your end.
Hope this helps.
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05-28-2017, 12:31 PM
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As far as keeping the GBCM (since it seems like no one has been able to successfully delete it without simply defaulting to the 13.8v charging), can I simply loop the GBCM through any somewhat large ground wire/cable on the car? The battery on my car is on the opposite side of the car, so I am trying to see what my options are.
05-29-2017, 02:24 PM
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As far as keeping the GBCM (since it seems like no one has been able to successfully delete it without simply defaulting to the 13.8v charging), can I simply loop the GBCM through any somewhat large ground wire/cable on the car? The battery on my car is on the opposite side of the car, so I am trying to see what my options are.
I was in the same boat as you and just ran a ground wire through it. It seems to just sit at 13.8v. Battery stays charged though so I guess it's ok. Also, you must be Vietnamese with a last name like that? I spent a couple months there touring on motorcycles and loved it
05-29-2017, 02:43 PM
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I was in the same boat as you and just ran a ground wire through it. It seems to just sit at 13.8v. Battery stays charged though so I guess it's ok. Also, you must be Vietnamese with a last name like that? I spent a couple months there touring on motorcycles and loved it
From some further reading, it seems like the module needs to be on a wire that's connected directly to the battery to read properly, which your experience kind of reinforces.
I may try to go ahead and put it on the positive wire coming off of the alternator and see if that'll work.
04-17-2018, 04:36 PM
#12
Hey thanks, this helped me with trying to figure out what to do with my GCBM. That blue wire 5668 was making me nervous. The difference between my setup and yours is nothing from the GBCM ever went to the PCM. It seems like a standalone unit almost, minus the 5668 and the 6752, which goes to the ODB according to my diagram. The brown and grey from the alternator go directly into the GCBM module, which sort of makes sense. I was considering deleting this but seeing other people having problems after kept me from doing it. Oh and I forgot, mine is an 07 L33
I am hoping its not too late to revive this...I have an 06 GCBM and need to know how you solved this. Our systems only have 8 wires and they all go to GCBM. Just wanted to know if there was anything you needed to hook up to PCM?? LT1SWAP.com states to move the brown wire to a connector on PCM. Did you have to do any of that. Any info would be greatly appreciated on how to wire this up.
05-22-2018, 11:05 AM
#13
i am hoping its not too late to revive this...i have an 06 gcbm and need to know how you solved this. Our systems only have 8 wires and they all go to gcbm. Just wanted to know if there was anything you needed to hook up to pcm?? Lt1swap.com states to move the brown wire to a connector on pcm. Did you have to do any of that. Any info would be greatly appreciated on how to wire this up.
06-01-2018, 08:27 AM
#14
For those wishing to keep and maintain the GBCM PCM programming and GBCM function for your '05 5.3L Vortec (Non-Hybrid) engine application, this may help. It may be applicable to other year and CID models too.
The GBCM was put in place to control the alternator charging behavior to improve engine fuel economy, performance and cut down on wear & tear of the alternator. The fact it is still an OEM feature says a little about the validity of purpose. I've read plenty "How to Delete" posts but none with the basic information about how to "Keep" and connect the GBCU wiring. After a good deal of research through wiring diagrams in AllData, here's what I've learned.
The GBCU Connector has 10 Pins.
Pin's A & C (Red/White) (Circuit 4740) are both positive battery voltage supply wires; 10 amp fused battery feeds to the GBCM.
Pin B (Gray) (Circuit 23) is the Generator Field Duty Cycle Control wire; connects to the OEM alternator plug; one of two wires. This wire is also spliced / tied to the PCM Green connector Pin #75; the Generator Field Duty Cycle Signal. In short, there is no need to alter these connections in the OEM harness.
Pin D (Brown) (Circuit 25) is the Charge Indicator Control wire; connects to the OEM alternator plug; the second of two wires. There is no need to alter this connection in the OEM harness.
Pin E is not used; a cavity.
Pin's F & H (Black/White) (Circuit 451) are both Ground wires; connect to the OEM harness ground Splice Pack and ultimately are grounded to the engine block. There is no need to alter this connection in the OEM harness.
Pin G (Dark Blue) (Circuit 5668) is the "Engine On" signal for the Power Brake Supplemental Brake Assist (SBA) Pump Motor. The SBA unit uses this wire to determine if the engine is running so it can run its initial start-up diagnostic features. For more info on the SBA pump and its operation, Google it. Otherwise this circuit is not needed for the GBCM operation and can be properly stowed or removed if the Supplemental Brake Assist System is not part of your application.
Pin J (Purple) (Circuit 5428) is the Generator Regulator Control wire. Connects to the PCM Green connector Pin #15. There is no need to alter this connection in the OEM harness.
Pin K (Orange/Black) (Circuit 6752) is the Class 2 Serial Data wire. Connects to the main splice pack (SP205) for Pin 2 of the OBD2 Data Link Connector. There are numerous OEM Class 2 Serial Data wires from various vehicle modules that connect to the OBD2 main serial data wire. There are also some that do not; like PCM Blue connector Pin 59.
I hope everyone finds this information helpful.
The GBCM was put in place to control the alternator charging behavior to improve engine fuel economy, performance and cut down on wear & tear of the alternator. The fact it is still an OEM feature says a little about the validity of purpose. I've read plenty "How to Delete" posts but none with the basic information about how to "Keep" and connect the GBCU wiring. After a good deal of research through wiring diagrams in AllData, here's what I've learned.
The GBCU Connector has 10 Pins.
Pin's A & C (Red/White) (Circuit 4740) are both positive battery voltage supply wires; 10 amp fused battery feeds to the GBCM.
Pin B (Gray) (Circuit 23) is the Generator Field Duty Cycle Control wire; connects to the OEM alternator plug; one of two wires. This wire is also spliced / tied to the PCM Green connector Pin #75; the Generator Field Duty Cycle Signal. In short, there is no need to alter these connections in the OEM harness.
Pin D (Brown) (Circuit 25) is the Charge Indicator Control wire; connects to the OEM alternator plug; the second of two wires. There is no need to alter this connection in the OEM harness.
Pin E is not used; a cavity.
Pin's F & H (Black/White) (Circuit 451) are both Ground wires; connect to the OEM harness ground Splice Pack and ultimately are grounded to the engine block. There is no need to alter this connection in the OEM harness.
Pin G (Dark Blue) (Circuit 5668) is the "Engine On" signal for the Power Brake Supplemental Brake Assist (SBA) Pump Motor. The SBA unit uses this wire to determine if the engine is running so it can run its initial start-up diagnostic features. For more info on the SBA pump and its operation, Google it. Otherwise this circuit is not needed for the GBCM operation and can be properly stowed or removed if the Supplemental Brake Assist System is not part of your application.
Pin J (Purple) (Circuit 5428) is the Generator Regulator Control wire. Connects to the PCM Green connector Pin #15. There is no need to alter this connection in the OEM harness.
Pin K (Orange/Black) (Circuit 6752) is the Class 2 Serial Data wire. Connects to the main splice pack (SP205) for Pin 2 of the OBD2 Data Link Connector. There are numerous OEM Class 2 Serial Data wires from various vehicle modules that connect to the OBD2 main serial data wire. There are also some that do not; like PCM Blue connector Pin 59.
I hope everyone finds this information helpful.
06-01-2018, 11:26 AM
#15
This is great, and thank you for posting, however I have an 06. still about a month away from dropping the motor in, but 06 had no wires going to the PCM from the GBCM..none at all. It looks to be a self contained unit. Still looking for my answers above 
Thanks again.
Thanks again.
06-03-2018, 07:02 AM
#19
Sorry for the late response, and thank you for your help BTW.
According to the GM diagram, we have
- 2 going to battery positive, Both Red/White
- 2 going to alternator (Gray and Brown)
- 1 going to Brake warning System - Dark Blue (this is the one I know from this post I don't have to worry about and can eliminate)
- 2 Black/White going to ground
- 1 Orange/Black "This is the only wire in question for me" According to the schematic from GM Wiring, this goes to the Class 2 Serial Data A6 Instrument Cluster (???) Any suggestions?
According to the GM diagram, we have
- 2 going to battery positive, Both Red/White
- 2 going to alternator (Gray and Brown)
- 1 going to Brake warning System - Dark Blue (this is the one I know from this post I don't have to worry about and can eliminate)
- 2 Black/White going to ground
- 1 Orange/Black "This is the only wire in question for me" According to the schematic from GM Wiring, this goes to the Class 2 Serial Data A6 Instrument Cluster (???) Any suggestions?
06-03-2018, 07:12 AM
#20
Sorry, forgot to add: According to "Fivetears" above, (Orange/Black) (Circuit 6752) is the Class 2 Serial Data wire. Connects to the main splice pack (SP205) for Pin 2 of the OBD2 Data Link Connector. Does this mean I can just go ahead and not worry that this wire is going to the instrument cluster, and I can just go ahead and connect it to the Pin 2 of the OBD2 connector??? If that is all, then my mystery is solved. Thanks!