I am in desperate need for some help to get my 99 c5 up and running again. I had just installed a new aftermarket stereo in the car when I noticed the hatch would not release, the windows, courtesy light, the remote, and fog lights all do not function along with a no crank condition. This is obviously a condition related to the BCM.

I am guessing that when I used a test light to probe the factory radio connectors I might have fried the BCM or erased its programming. After doing some research I used the constant hot and switched hot and ground from the plug near the fuse block for my stereo, which functions normally. I also used the factory speaker wires from the factory plug at the radio. Does this tie into the BCM also?

The car is showing a few codes they are 40 no communication, 58 SDM, U1000 H C, U1040 H, U1064H C, 60IPC U1160HC, U1176 H C, A1 RDCM, U1064H.

I have checked all of the fuses inside and underhood, and checked and cleaned all grounds pretaining to the BCM. I did notice that 3 incabin fuses do not get powered at all, number 26 hatch trk, 2 monitored ld, 24 radio antenna. I have tried swapping the relays above the BCM with no change. I grounded the yellow and black wire on the start relay and the engine would crank. I tried the relearn procedure twice, and I checked both door connectors. Ive also checked the two star connectors by the bcm and the underhood ground plug under the battery box.

Im pretty sure I need a new BCM but would like to test the power wires to the BCM before I purchase one. I know the BCM fuses have power but dont know which wires at the BCM connector should have voltage. Also is it possible to have a used BCM erased and reprogrammed? Any help would be appreciated, as I am out of ideas.

 

Did you try disconnecting the battery for a few minutes?

 

First, I would confirm you checked all BCM fuses, and appropriate voltage/ground checks at the BCM connectors...with a DMM..not a test light.

Did you actually use the correct adapter for the radio wiring so it was plug and play with your aftermarket unit, or did you just splice into the factory harness? Reason I ask, is wondering what happens if you put the factory radio back in?

Finally, there is never a need to just "probe around" when you have the schematics.

 

Did you hook anything to the Serial Data line,Pin #15 that I've marked on the schematic. If so, disconnect it and try it.

 

I have had the battery disconnected serveral times, and I am positive that all bcm fuses are good. I have cut and spliced the factory speaker wires to the new unit. The aftermarket stereo has plugs which I had unplugged with no effect. I would assume the car would run with the factory radio unplugged. I had mentioned in my post that I dont know which wires at the BCM connector should have voltage, or ground, so no I did not check the BCM wires yet.

 

I had to replace the BCM in my 2000 due to it getting wet. I bought a used one from E-bay for $150 and did the handshake thing and it starts/runs/drives perfectly with all options working properly including the HUD. I may have gotten lucky in getting a BCM from an identically optioned car but don't know for sure. I never had the car hooked to a scanner or anything, just the handshake thing and all is great. I also have an aftermarket radio in the car that has had the wires cut and spliced with no problems. Only have a DIC code that says no comm with the radio. After lots of research on the problem I had, it is my understanding that a used BCM can be reprogrammed if you need to. Good luck with your problem. BTW, I fried a BCM on a Tahoe hooking up a stereo when I dropped a live wire I was probing on a metal bracket.

 

Some BCM Info :
BCM +12V power feeds
Fuse #25 = BCM Logic Power Feed
Fuse #23 +Power feed for 12V BCM Drive outputs (CL)
Fuse #13 = 12V switched from ignition switch (ON, and START positions)
Fuse #9 = 12V from Ignition switch ON and ACC position)

BCM grounds
A9-C1 connector pin Logic Ground
A2-C3 Power Drive Ground

BCM Functions
Traction control switch (sends switch signal to TCM)
Automatic headlamps
Parklamps
Headlamp doors
DRL
Turn signal control
Fog lamp control
Dash light dimming function (HVAC control, console lamp,PRNDL lamp,
Back-up lamp flash when locking/unlocking
Monitored load control (underhood lamp, glove box lamp, vanity mirror lamps, map light)
Interior courtesy lamps
Antitheft horn alarm and TDR (starter cutoff) control
Vehicle Antitheft PassKey circuit
Rear window defogger
Horn
Colum Lock
Hatch release and ajar warnings for (or convertible top cover release)
Key in ignition warning chime
Driver door key unlock signal (disarms antitheft horn alarm)

Troubleshooting info for the C5 serial-data-bus : (by ersatz928)

Every module which talks on the serial bus has it own piece of wire which comes to a"star" junction. The star junction is where all the wires connect together, so all the modules can talk to each other. There are actually physically two star junctions, located next to each other, to the left of the BCM module. There are two because GM needed more wire connections than one star junction block could handle, there is a short wire that connects the two star blocks together. Each star is a black (or grey?) rectangular plastic block, with lots of wires on one side. It is really just a multipin connector which is plugged-into a shorting socket, which connects all the wires together.

C5 modules (and the databus wire color) on the serial-bus are :
BCM (Light Green)
PCM (Dark Green)
IPC Instrument Cluster (Gray)
DDM Driver Door Lock Module (also controls the window) (Brown)
PDM Passenger Door Lock Module (also controls the window) (Tan)
Radio (but not the CD Changer) (Orange)
Auto-Climate control head-unit/display (Option) (White)
RCDLR (Radio receiver for the Key-Fob transmitter and Tire Pressure sensors) (Pink)
SCM module for Memory Power Seats and telescope colum (Option) (Brown white stripe)
ESC Electronic suspension shock damping control module (Option) (Dark Blue with white stripe)
EBCM Traction Control/AH module (Light Blue)
SDM (Airbag control) module (Dark Blue)
The Star Bus also has a connection at the Data Link Connector (under the drivers side dash) where you connect a OBD2 code scanner to. DLC pin #2 (Purple wire)

There are three kinds of failures that can take down the whole data-bus :
1) One of the wires is shorted to ground, somewhere along its length between the star junction and the module location.
2) One of the modules has an internal bus-driver/receiver failure which forces a continious positive voltage on the bus.
3) One of the modules has an internal bus-driver/receiver failure which forces a continious low voltage (short to ground) on the bus.

This troubleshooting assumes there is only one shorting problem with the data bus wiring, or one module.
1) Disconnect the battery
2) Use an Ohm-meter (DVM, DMM, VOM..) to measure the resistance between DLC pin #2 (Purple wire, upper row, the pin to the left of the rightmost pin), and to chassis ground DLC pin #4 (Black wire, upper row, fourth pin to the left of rightmost pin). I think the measured resistance should be 5K (5000) Ohms or greater. If it measures at least 5000 ohms, you don’t have a short-to-ground on the data bus. If it is less than 5000 ohms got the next step. NOTE : I need to verify the 5000 Ohm go/nogo resistance.
3) Unplug the 2 BCM connectors. If the low resistance goes to 5000 ohms, the problem is internal to the BCM module, replace it. If the low resistance remains, re-install the BCM connectors and goto the next step.
4) Unplug the shorting socket from both Star connectors. Use your ohmeter to probe one wire at a time, to find the low resistance to ground. Identify the offending bus-wire and/or module by using the wire color associated with each module (see the module list above). 5)Find and unplug the module you identified in step 4. If the low resistance goes away, then that module has an internal short. If the resistance stays low, then the short is in the wire itself, somewhere between the Star block and the module location.

Note : The wire colors are from my 2001 factory service manual, I have not verified that they are the correct colors at the star connector blocks , or if they apply to all model year C5s.

---------------------------------------------------------------------

 

After looking at ersatz928"s post, I see that Pin #16 is also a "Serial Data" wire, check it also. It's important to not have anything connected to the Serial Data circuit.

 

Thanks ersatz928, for the info, I assume that is from a factory service manual. I performed the test outlined, and was not able to find any low resistance circuits. However I was able to trace the power leads from the fuse box to the BCM connectors, and the associated grounds at the plugs. I have continuity from the fuses to plugs and have 0 resistance at the plug grounds to chassis ground.

So I am reasonable sure that my BCM is bad. I contacted my local chevy dealer and was quoted $1380. Oriely has one for $600, I will probaly try to locate a used part somewhere.

 

ACDELCO 9381399 [MODULE-BODY CONTROL] MODULE,BODY CONT OEM#09381399 0.00 $234.83
Not sure if this is the correct part but its the one shown for a '99 without the elect. suspension

 

That price is outragous the price of a new BCM part from Gene at GMPartshouse is around 230. plus. I had to replace mine because of a water leak on the pass side because of the clogged water drain.

 

That price includes dinner, a massage, and one orgasm....right?

 

Thanks guys for your input. Got the car running today with a used BCM from vette2vette. After I plugged it up I knew the car was fixed when I saw my courtesy lights come on. I did the key relearn sequence and the car started right up. Back in business!!

 

LMAO!! Thats a good one!!

Glad to see that you got it fixed. Save that old BCM because you might have another issue that may come back.

That BCM may still be good! Now that the car is runnin again, plug that old one back in and see if the problem reappears!

BC