‘97 vette weird electrical issue
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Cruising
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‘97 vette weird electrical issue
I’ve been battling an electrical issue with my ‘97 where my interior lights, fog lights, and DRL’s all flash. It happens when I have my parking lights or headlights are on. Relays 42, 37, 38, and 40 in the passenger footwell fuse box and relay 39 in the engine compartment click when the lights flash. I put a new battery in the car about a year and half ago and I’ve cleaned all the grounds except the interior ones which i will get to as soon as I can. All the original incandescents have been swapped with LED’s. I’m not really sure where to go from here. My volts on the DIC typically are between 13v and 13.5v. Any advice is appreciated. If any further information is wanted let me know.
Tech Contributor
Joined: Jan 2007
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From: Dyer, IN
I’ve been battling an electrical issue with my ‘97 where my interior lights, fog lights, and DRL’s all flash. It happens when I have my parking lights or headlights are on. Relays 42, 37, 38, and 40 in the passenger footwell fuse box and relay 39 in the engine compartment click when the lights flash. I put a new battery in the car about a year and half ago and I’ve cleaned all the grounds except the interior ones which i will get to as soon as I can. All the original incandescents have been swapped with LED’s. I’m not really sure where to go from here. My volts on the DIC typically are between 13v and 13.5v. Any advice is appreciated. If any further information is wanted let me know.
Any codes? Did this problem start after you swapped the incandescent bulbs for leds? Any water leaks recently in the passenger footwell, or moisture in that area?
Thread Starter
Cruising
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All the relays you listed have 12 volts at all times on one side of the relay coil. The common denominator is the BCM, which supplies a ground to the relay coils to energize them. So the BCM causing the issue, the question is.....why?
Any codes? Did this problem start after you swapped the incandescent bulbs for leds? Any water leaks recently in the passenger footwell, or moisture in that area?
Any codes? Did this problem start after you swapped the incandescent bulbs for leds? Any water leaks recently in the passenger footwell, or moisture in that area?
Tech Contributor
Joined: Jan 2007
Posts: 19,493
Likes: 1,178
From: Dyer, IN
I’m not sure on codes, i’ll check them asap and write up another reply with them. The problem has been pretty consistent across the entire time i’ve owned it (about 2 years) and i’ve slowly been swapping to LED’s so i’m not 100% sure that it isn’t the LED’s but I also can’t say that it is. I did have to resolve some leaks a while back. The dealer I got it from had it sitting outside without the windows sealing well. I was also thinking it could be a BCM issue but I wanted to get a second opinion on the situation before I buy a new one.
Thread Starter
Cruising
Joined: Apr 2025
Posts: 10
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All the relays you listed have 12 volts at all times on one side of the relay coil. The common denominator is the BCM, which supplies a ground to the relay coils to energize them. So the BCM causing the issue, the question is.....why?
Any codes? Did this problem start after you swapped the incandescent bulbs for leds? Any water leaks recently in the passenger footwell, or moisture in that area?
Any codes? Did this problem start after you swapped the incandescent bulbs for leds? Any water leaks recently in the passenger footwell, or moisture in that area?
Tech Contributor
Joined: Jan 2007
Posts: 19,493
Likes: 1,178
From: Dyer, IN
You have been driving the car with all this going on?
Thread Starter
Cruising
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The U1040 is telling you that the EBTCM lost communication on the serial data line. Whatever is causing that is why you are getting the ABS/TCS issues. The BCM does control relay 37 (ABS/TRNS) in the underhood electrical center, which supplies 12 volts to the EBTCM. You have also have codes for the rear defog circuit and right DRL circuit....controlled by the BCM. The B2721 is a pass-key failure, and being current will keep the engine from cranking.
You have been driving the car with all this going on?
You have been driving the car with all this going on?
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Tech Contributor
Joined: Jan 2007
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From: Dyer, IN
There is a strong chance the BCM is the issue, but before replacing the BCM....due diligence is required with 12volt and ground checks to make sure the BCM has the necessary input to operate. If you have a DMM/test-light and schematics this is easily accomplished...if not, it may be best to take it to a trusted auto electric shop.
I will add that if 12v or ground to the BCM were intermittent, I would expect to see a U1064 codes as well.
Thread Starter
Cruising
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Used to be called VATs in a C4, then GM called it PASS-key starting with the C5. The resistor bypass is used when the lock cylinder no longer reads the resistor pellet on the key. That will not help you if the BCM is at fault, and not reading the resistance.
There is a strong chance the BCM is the issue, but before replacing the BCM....due diligence is required with 12volt and ground checks to make sure the BCM has the necessary input to operate. If you have a DMM/test-light and schematics this is easily accomplished...if not, it may be best to take it to a trusted auto electric shop.
I will add that if 12v or ground to the BCM were intermittent, I would expect to see a U1064 codes as well.
There is a strong chance the BCM is the issue, but before replacing the BCM....due diligence is required with 12volt and ground checks to make sure the BCM has the necessary input to operate. If you have a DMM/test-light and schematics this is easily accomplished...if not, it may be best to take it to a trusted auto electric shop.
I will add that if 12v or ground to the BCM were intermittent, I would expect to see a U1064 codes as well.
