No running lights or high beams
Thread Starter
Burning Brakes
Joined: Apr 2023
Posts: 1,087
Likes: 392
From: Florida
2025 C6 of the Year Finalist - Unmodified
No running lights or high beams
Today i noticed my drl’s are not coming on along with the sidemarkers. The tail lights, brakes, signals, everything works except I also noticed no hi beams. I checked the 10a fuse #8 i believe which is also for the bcm and the relay below it as well. I swapped the relays around and still no difference. Checked the hi beams fuses and all seems fine as well. Is there another relay or fuse somewhere i’m missing? Funny part is this am I pulled the #8 fuse because as stated I believe it is also for the bcm and when my gas gauge acts up, pulling this fuse seems to reset it for a bit. What could have happened here? I swear when you would hit the unlock button in the remote, the parking lights and side markers would stay on a few seconds and would hear the relay click on and off. No such sounds of relays at all anymore… any ideas?
Thread Starter
Burning Brakes
Joined: Apr 2023
Posts: 1,087
Likes: 392
From: Florida
2025 C6 of the Year Finalist - Unmodified
It’s a 2007 base. Everything works fine except the drl’s, sidemarkers and hi beams. The sidemarkers work when the headlights are on. I did wash the car last night but not under the hood or anything… I can read wiring diagrams but i’m not the greatest with electrical diagnostics.
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,628
Likes: 4,071
From: Cape Coral, Florida
It’s a 2007 base. Everything works fine except the drl’s, sidemarkers and hi beams. The sidemarkers work when the headlights are on. I did wash the car last night but not under the hood or anything… I can read wiring diagrams but i’m not the greatest with electrical diagnostics.
Thread Starter
Burning Brakes
Joined: Apr 2023
Posts: 1,087
Likes: 392
From: Florida
2025 C6 of the Year Finalist - Unmodified
Thanks, yeah all side markers are out until the headlights come on. The front running lights work when the headlights are in as well. Rear tails have led bulbs, the front drl’s are stock bulbs. Been fine with this setup for awhile now… thanks again
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,628
Likes: 4,071
From: Cape Coral, Florida
Just to see if your high beams come on can you jumper terminals 30 and 87 of the high beam relay 39…the load side is “hot at all times” so you don’t have to do anything with the ignition…when you jump those 2 the high beams should turn on…if this may be over your head guiding you step by step to diagnose this would be next to impossible…may be time to seek out an auto electric shop in your area…and don’t worry about being good at electrical diagnostics…99.99% of professional mechanics whether at a repair shop or dealership are in the same boat as you.
Last edited by C5 Diag; Nov 8, 2024 at 05:11 PM.
Thread Starter
Burning Brakes
Joined: Apr 2023
Posts: 1,087
Likes: 392
From: Florida
2025 C6 of the Year Finalist - Unmodified
That I can certainly do… I’ll have to find a piece of wire tomorrow and try it. I used to jump the fan relay on my C5 at the track so this is cake. If no headlights jumping it, idk where to start next. It was fine before these two variables: washed the car prior night, pulled fuse #8 to reset bcm. I swear this happened once before when I first got the car and then the next am when it cooled off it worked again. Then it started working all the time… Looked into the issue and it appeared there was a recall on the low beam but nothing for the high beam. I don’t think this car has had any recalls even done to my knowledge. I asked the gm dealer about any tsb’s or recalls on the car and they said it’s been to long for them to honor it.
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Moderator, Tech Contributor
Joined: Sep 2013
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From: Cape Coral, Florida
You’ll be jumping the “load” side of the relay….pins 85 and 86 are the “control” side…every relay has 2 power sources…if you have a test light the other terminal which is closest to the fender should also have power…the 4th terminal goes to the BCM so we can check that later.
Thread Starter
Burning Brakes
Joined: Apr 2023
Posts: 1,087
Likes: 392
From: Florida
2025 C6 of the Year Finalist - Unmodified
Thank you for the diagrams, I will study those! This am I went outside and tried the running lights, nothing. Went for a ride and noticed in the ride home they are back on and the high beams working. I have an aftermarket kenwood (non bose stock) with the pac audio harness. Since install the radio is hit or miss turning on with the ignition, sometimes you have to turn it off and back on. Noticed the door/ignition chime was going off double yesterday when the lights were giving me issues… hope the bcm isn’t going bad. I’m assuming it’s one of the following: fuse block, bcm, radio issue, issue with led bulbs. I had installed radioflyer’s led bulbs all around a year ago and had to remove them because they overheated and were causing electrical issues. Parking lights etc went out then… Thats why i switched back to the stock bulbs in front but went with some led’s inside the stock tails.