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Recently acquired a 2000 C5 at a good price that is cosmetically perfect and already had a lot of performance mods. Trying to sort out some electrical issues and started checking the basics - fuses, relays, etc., and I came upon this mess by the BCM. Several of the wires from the bottom connector of the BCM have been snipped and tied into this aftermarket bus bar which is then grounded to the BCM case. Any idea why someone would do this? Are several of the wires going to this connector ground wires and they were trying to correct some grounding issue? Also there are two orange wires laying loose by the fuse box. Wondering if these used to be connected originally and were clipped for some reason. Previous owner said his mechanic must've done it. Can't understand anyone hacking up a wire harness in this manner.
It's hard to tell in that mess exactly what is what. Stretch the buss bar out from the BCM so all the wires can be identified.
Here's a better pic with the wire colors clearly displayed. Any idea what all the ground wires would go to or where they would've originally been connected? Right now, they're all landed on that aftermarket bus bar which is grounded to the door jamb.
Here's a better pic with the wire colors clearly displayed. Any idea what all the ground wires would go to or where they would've originally been connected? Right now, they're all landed on that aftermarket bus bar which is grounded to the door jamb.
Do any of the wires to the buss bar have stripes besides the blue wire?
Ok. From what I can tell, it looks like someone has replaced star connector #1 with the buss bar. It can't be grounded, otherwise nothing would work. The question is.....where does the black wire actually connect to?
Ok. From what I can tell, it looks like someone has replaced star connector #1 with the buss bar. It can't be grounded, otherwise nothing would work. The question is.....where does the black wire actually connect to?
That black wire on the end of the bus bar was grounded to the door jamb. Disconnected that black wire and now all my gauges, power windows, mirrors and locks work! At least I'm making some progress on all these electrical gremlins. Before uncovering this mess I had already checked the connections in door accordian boots thinking there was a fault there preventing all the door functions from working and causing my gauges to freak out.
Before I disconnected that ground wire, it would start and run perfectly. After disconnecting that ground wire, the car will start, runs for about 3 seconds, then turns off. I also get the flashing SECURITY warning on the dash. I suspect one of those wires that's landed on that bus bar might actually need to be grounded to make the VATS function properly. I suspect a problem with the VATS might be why the previous owner hacked up these wires. There is a VATS bypass module installed by the steering column though so I would think the VATS should be fully disabled.
Last edited by Sarasota C5; Apr 10, 2026 at 01:01 AM.
That black wire on the end of the bus bar was grounded to the door jamb. Disconnected that black wire and now all my gauges, power windows, mirrors and locks work! At least I'm making some progress on all these electrical gremlins. Before uncovering this mess I had already checked the connections in door accordian boots thinking there was a fault there preventing all the door functions from working and causing my gauges to freak out.
Before I disconnected that ground wire, it would start and run perfectly. After disconnecting that ground wire, the car will start, runs for about 3 seconds, then turns off. I also get the flashing SECURITY warning on the dash. I suspect one of those wires that's landed on that bus bar might actually need to be grounded to make the VATS function properly. I suspect a problem with the VATS might be why the previous owner hacked up these wires. There is a VATS bypass module installed by the steering column though so I would think the VATS should be fully disabled.
Just to be clear....NONE of the wires for the serial buss should be grounded. You need to find the other Star connector....or what is left of
Not to split hairs, but there is no "VATS" on a C5....it's called "PassKey" if you are looking in your service manual under Theft Deterrent. If the engine cranks, you do not have a problem with the PassKey detection(key resistance). Nothing is "grounded" to the PassKey detection circuit for the BCM.
You will have to discover which wire that is connected to the buss bar has to be connected to ground. The wires that were originally connected to the star connector have to be connected together in order for the various modules to be able to communicate with each other.
You will have to discover which wire that is connected to the buss bar has to be connected to ground. The wires that were originally connected to the star connector have to be connected together in order for the various modules to be able to communicate with each other.
What are you talking about? All the wires on the buss bar are for the serial buss. None of those wire should be grounded.
I agree, but why would someone connect all the seriel buss wires to ground? Why does the car start and run for a few secounds and then stall after removing the ground wire? Only the previous owner might shed some light on this problem. I am out!!
Wild guess: the car was reporting issues to the DIC via the communication bus, and defeating the bus made the DIC stop complaining. Didn't solve the underlying issues, of course. It just made the issues appear to be resolved.
If those really are all communication lines (I didn't check) then it would be interesting to disconnect the ground wire from the bus bar (so that the modules can talk to each other) and then read the diagnostic codes.
The troubleshooting continues. After so many comments in various forums about low battery voltage causing the BCM and other systems to have fits, I verified battery voltage was 11.8 and replaced the battery. It started and ran continuously without stalling out. I tried this 2 more times and it started and ran just fine. I thought I had it solved. On the fourth start, it ran about 3-5 seconds and the turned off. Now it keeps turning off after 3-5 seconds every time. It seems like something is cutting the fuel. I would guess that having the battery disconnected for a bit reset something in the BCM and after being energized for a while, it has "relearned" whatever the fault was and I'm right back where I started.
One other peculiar issue noted when tracing wires. Someone installed both the LMC5 Column Lock Module from Complianceparts.com on the BCM AND a Column Lock Simulator from LS1howto.com under the steering column. I would imagine this could be giving the BCM fits. I get both the Service Column soon and Remove Key for 10 seconds warnings. I requested installation instructions from Compliance Parts to ensure it was installed correctly in the first place.
Last edited by Sarasota C5; Apr 14, 2026 at 11:59 PM.
As long as the LMC5 is installed properly there is no reason for a Column lock simulator .
This is how my LMC5 is installed and have been working perfect for 11 years on my 2000
The troubleshooting continues. After so many comments in various forums about low battery voltage causing the BCM and other systems to have fits, I verified battery voltage was 11.8 and replaced the battery. It started and ran continuously without stalling out. I tried this 2 more times and it started and ran just fine. I thought I had it solved. On the fourth start, it ran about 3-5 seconds and the turned off. Now it keeps turning off after 3-5 seconds every time. It seems like something is cutting the fuel. I would guess that having the battery disconnected for a bit reset something in the BCM and after being energized for a while, it has "relearned" whatever the fault was and I'm right back where I started.
One other peculiar issue noted when tracing wires. Someone installed both the LCM5 Colum Lock Module from Complianceparts.com on the BCM AND a Column Lock Simulator from LS1howto.com under the steering column. I would imagine this could be giving the BCM fits. I get both the Service Column soon and Remove Key for 10 seconds warnings. I requested installation instructions from Compliance Parts to ensure it was installed correctly in the first place.
I would remove the CLS so you are as close to the original configuration as posssible.
I would also STOP trying to start the car until you have sorted out the wiring. It was recommended to find the other Star connector and see how it is connected? Did did you do that? I see a Star connector in the picture behind the buss bar.....what is connected to the Star connector?
Thanks for providing the LMC5 instructions. I checked the other Star connector and that's wired properly. Removed the CLS module from under the steering column and the Service Column and Remove Key for 10 Seconds warnings remained. Focused my attention on verifying proper installation of the LMC5. Verified everything twice, then the "Optional" section on page 2 caught my eye. Sure enough, the previous owner or mechanic had installed the brown wire in the connector, but had not clipped the brown looped wire. I clipped the brown loop and knew I was on to something when I turned the key and the Service Column and Removed Key for 10 Seconds warnings were gone. Car starts right up and continues running each time. When troubleshooting, always start at the beginning and restore the system to original as best you can and start every procedure from scratch.
I did find a couple more random wires that were clipped and tucked behind the dash, so I'll be tracing those next and then on to troubleshooting the cooling fans. Making some progress.
Thanks for providing the LMC5 instructions. I checked the other Star connector and that's wired properly. Removed the CLS module from under the steering column and the Service Column and Remove Key for 10 Seconds warnings remained. Focused my attention on verifying proper installation of the LMC5. Verified everything twice, then the "Optional" section on page 2 caught my eye. Sure enough, the previous owner or mechanic had installed the brown wire in the connector, but had not clipped the brown looped wire. I clipped the brown loop and knew I was on to something when I turned the key and the Service Column and Removed Key for 10 Seconds warnings were gone. Car starts right up and continues running each time. When troubleshooting, always start at the beginning and restore the system to original as best you can and start every procedure from scratch.
I did find a couple more random wires that were clipped and tucked behind the dash, so I'll be tracing those next and then on to troubleshooting the cooling fans. Making some progress.
BCM Hack Job Wiring
