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Old 08-02-2014, 11:47 AM   #1
TarHeelDan2001
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Default BCM Issues - Please help

Car is a 2002 MN6.

I was driving down the road yesterday, and all of a sudden all interior lights in the car just came on (and could not be shut off) and the DIC started displaying miscellaneous errors like "Door Ajar" and "Hatch Ajar" (neither were open). The key-in-ignition dinging noise now occurs continuously, regardless of whether the key is in the ignition, doors open or closed, etc. There is also a relay in the passenger footwell area that clicks continuously when the car is not running. I have unhooked the battery to keep all of this craziness from draining the battery.

I know low voltage can cause the electronics in these cars to go haywire. The battery is an Optima Red Top that is less than 2 years old. When tested with a multi-meter with the negative cable unhooked, the voltage came back around 15V.

I pulled the following BCM codes, and cleared them:

B0432 H (Rear Defogger Relay Circuit)
B0502 H (RH DRL Relay Circuit)
B0507 H (LH DRL Relay Circuit)
B2527 H (Horn Relay Circuit)
B2587 H (Column Lock/Unlock Drive (A))
B2592 H (Column Lock/Unlock Drive (B))

These were the only codes displaying. I also got the "Pull Key, Wait 10 seconds" message on the DIC. After clearing the codes and starting the engine, this message has not returned yet.

I had the dreaded column lock issue in 2009 w/ 61,000 miles on the car, and the dealer removed the locking collar and installed the K harness. Shortly after that, I removed the K harness and installed the Corvettes of Houston CLB. The car has 107,000 miles on it now.

I checked the 3 BCM fuses in the footwell, and all seemed to be fine. There was no obvious water intrusion, corrosion, etc. anywhere near the BCM.

The car seems driveable (no fuel cutoff), but obviously this is something I need to fix as soon as possible because of the battery drain issue.

I'm traveling away from home, and I called 5 dealerships in the area, and none of them has a Corvette tech working today.

Any troubleshooting help would be greatly appreciated.
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Old 08-02-2014, 01:32 PM   #2
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Try disconnecting the serial data bus connectors (2 thin connectors left of BCM)

That might refresh the BCM
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Old 08-02-2014, 02:49 PM   #3
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I just took the battery to have it tested because 15V seemed high. I think the multimeter I was using was just inaccurate because AutoZone said the battery checked out just fine. I reinstalled the battery and drove it about 5 miles. The door chime stops when the engine is running, but the interior lights will not turn off. Other than the interior lights, everything seems fine while driving. As soon as the engine is turned off, the relay clicking from the passenger footwell starts again, the door chime restarts and continues intermittently, and the interior lights remain on. Locking the car with the key fob seems to affect the speed of the door chime sound, but the interior lights remain on.

I just checked for new codes, and I have no codes across the board.

The battery has been disconnected for extended periods of time, so I would think that would be sufficient to reset the BCM (and other systems).

Would a failing relay in the BCM cause all of these problems? Do I just need to replace the BCM? I am baffled.
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Old 08-02-2014, 03:17 PM   #4
Bill Curlee
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One of TWO things could be wrong. Check for both:

The BCM got wet form HVAC Condensate or rain or car wash water. See if the BCM or the carpet and Jute Underlayment is damp.

OR

You have a serial data buss corruption issue. Find the STAR connection to the LEFT of the BCM with FOUR WIRES.

Pop off the top shorting buss and see if the issue goes away.

If it does or doesnt post results.

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Old 08-02-2014, 04:22 PM   #5
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Thanks, Bill. I really appreciate your help on this. I have also been reading this troubleshooting thread you authored:

http://forums.corvetteforum.com/c5-t...-there-is.html

I removed the top of the shorting buss, reconnected the battery and started the car. The interior lights remained on. After I shut off the engine, the relays in the BCM started clicking immediately. The relay clicking is definitely coming from the BCM because when I put my hand on it, I could feel the vibration from the clicks.

This is the shorting buss I removed:

Click the image to open in full size.

There are 4 wires there... it's just hard to see the black on against the black carpet.

I also checked the codes after turning off the engine, and I had a new HVAC U1160 HC code. Presumably this new code is from removing the shorting buss.

I also checked the area around the BCM, and it's bone dry. I also removed the BCM, and checked both sides of the board for condensation or evidence of damage or corrosion. Everything looks good to the naked eye. Not even any dust. I was very careful handling the board to avoid static.

Should this process be repeated with Star Connector 1?
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Old 08-02-2014, 05:37 PM   #6
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Quote:
Originally Posted by TarHeelDan2001 View Post
Thanks, Bill. I really appreciate your help on this. I have also been reading this troubleshooting thread you authored:

http://forums.corvetteforum.com/c5-t...-there-is.html

I removed the top of the shorting buss, reconnected the battery and started the car. The interior lights remained on. After I shut off the engine, the relays in the BCM started clicking immediately. The relay clicking is definitely coming from the BCM because when I put my hand on it, I could feel the vibration from the clicks.

This is the shorting buss I removed:

Click the image to open in full size.

There are 4 wires there... it's just hard to see the black on against the black carpet.

I also checked the codes after turning off the engine, and I had a new HVAC U1160 HC code. Presumably this new code is from removing the shorting buss.

I also checked the area around the BCM, and it's bone dry. I also removed the BCM, and checked both sides of the board for condensation or evidence of damage or corrosion. Everything looks good to the naked eye. Not even any dust. I was very careful handling the board to avoid static.

Should this process be repeated with Star Connector 1?


If you disconnect STAR 2, the car will not run. What does the IPC voltmeter on the dash and the DIC digital volt meter read with the key ON??

Find all the BCM fuses and read the test slots on top of the fuse to chassis ground. You should see battery voltage on all the BCM fuses (ignition ON)
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Old 08-02-2014, 06:16 PM   #7
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I disconnected Star 1 and Star 2, and ran a jumper wire between the PCM and the BCM serial wires. The engine started fine, but it immediately switched to reduced power. It also threw lots of U codes...I didn't write them all down. Interior lights remained on. I shut everything down immediately.

With Star 1 and Star 2 both connected and ignition on (engine off), the IPC and DIC voltage was reading 11.9V. I tested each of the 3 BCM fuses at the test slots, and voltage was around 15.6 V. I think the multimeter I borrowed is reading high, but it doesn't seem like I have a low/no voltage situation at any of the fuses.

After all of this, I am now getting the "Pull Key..." DIC error again as well as "Door Ajar" and "Hatch Ajar". Door chiming and interior lights on.
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Old 08-03-2014, 12:02 PM   #8
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This thing is killing me. I should be able to limp it back to Atlanta without a problem, and it's going to be the dealership's problem tomorrow. Fourth time in the shop for repairs in the last 6 months. The folks at Enterprise probably know my name at this point.
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