Anyone ever see this fault code? It sounds serious!

[clinebarger]

Not serious at all....

*Is the alternator charging?
*What is the battery voltage with the engine running?
*Are you running the factory 2005 alternator?
*Is the Regulator plugged in?

2005 1500's was the first year for the alternator control module, I generally segment swap these PCM's & run a 2500/3500 or 2004 & earlier 1500 alternator.

[Steve Cole]

Thanks for the quick reply Clinebarger!

As for your questions- I am running the factory 2005 alternator. I don't know if the battery is being charged by the alternator or what the battery voltage is while running because i have not run the motor more than a few seconds at a time because I don't have the radiator hooked up yet and I am trying to get the O/H tranny full of fluid, the cluster isn't installed yet etc. I just finished up the air intake yesterday. I wanted to figure out this fault code before I put the cluster in just in case it is a under dash wiring issue I need to correct.

You asked if the regulator was plugged in. I thought the alternator was internally regulated. Where is this regulator located? What about the Alt. control module, is it internal? TIA

[Steve Cole]

This HAS to be the reason for my fault code right? Nothing going to the battery. This is what happens when you stop working on something for a year then try to pick up where you left off!

[Steve Cole]

Originally Posted by clinebarger

Not serious at all


2005 1500's was the first year for the alternator control module, I generally segment swap these PCM's & run a 2500/3500 or 2004 & earlier 1500 alternator.

Hey Clinebarger,

Can you explain what you mean by segment swapping the PCM's and why you do that? Is the 2005 alternator prone to problems?

Thanks!

[truckdude239]

Originally Posted by Steve Cole

Hey Clinebarger,

Can you explain what you mean by segment swapping the PCM's and why you do that? Is the 2005 alternator prone to problems?

Thanks!

steve a segment swap is when they change part of the software in the ecm to run like something from a different year like in your case you dont have the alternator control module so the ecm is defaulting what it want the ecm to charge to 13.7v, if you have someone change the charging part of the computer software to say a 2004 alterantor software and use an 2004 alt then you proplay sovle most of your problems

[Steve Cole]

Thank you for that great explanation David, I get it now! About the alternator control module, is this something I should have taken from the donor truck?

I checked Auto Zone but they don't list one. I know where my donor truck is so I could go get it if I knew what it looked like. I figure this would be easier than trying to find someone to re-program my ECM.

[ls1nova71]

The GBCM is located on the negative battery cable, 6" or so from the battery terminal. There are several wires that go to it which can be easily hooked up, but there is one serial data wire that ties into the instrument cluster. I have never tried it, but have heard it will work without the instrument cluster wired in it.

[Steve Cole]

Originally Posted by ls1nova71

The GBCM is located on the negative battery cable, 6" or so from the battery terminal. There are several wires that go to it which can be easily hooked up, but there is one serial data wire that ties into the instrument cluster. I have never tried it, but have heard it will work without the instrument cluster wired in it.

Hi Eric,

You say that there are several wires that go to the GBCM, but where do they come from? It seems like GM over complicated things on a perfectly good system. That being said, I still need to get this fixed so I am looking for advice (from anyone) on the best way to handle this. Correct me if I'm wrong, but it seems like there are only two options here- re-program the ECM to charge a 2004 or earlier alternator or wire in a GBCM? Am I missing another option here?

TIA for anyone's help with this.

[ls1nova71]

There are 2 powers, 2 grounds and a few that go to the PCM. The only one you won't be able to hook up is the gray wire going to the dash. Just hook the orange and green wires together leaving out the gray and it should work. I had to upload the schematic in two pics, that's why it looks funny.