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Looking for some help diagnosing an electrical issue on my C6 GS. The rear lights will intermittently stop working while driving. When this happens, everything on the back end goes out at once — brake lights, blinkers, hazards, and rear side markers.
Setup & Background:
Running Morimoto Gen 2 tail lights + side markers (but I don’t think these are the root cause).
All fuses related to the lights have been checked and replaced.
I unplugged/replugged the two connectors under the far right passenger tail light.
Problem first started after washing the car (but I’ve never had moisture issues before).
No warning messages, I just notice it when my turn signal ticking sounds different.
What I’m trying to figure out:
I believe the issue may be the BCK/UP LAMP relay on the BCM. I hear it clicking so I don't know if it needs to be replaced but wanted to try that next
I know the BCM is located in the back, but I can’t figure out how to access the relay itself. Do I need to remove the 3 bolts holding the BCM and is the relay literally on the other side?
Other thoughts:
Could this be an adapter issue with the LEDs?
Could moisture have gotten into a connector somewhere?
I'd start with the easiest things first. Check all the connections that you changed, touched, or might have touched. Make sure they're all snug and secure. Especially grounds. As well make sure you have absolutely perfect grounds.
What year is the car ??…and yes the relay is on the underside of the BCM which is located in the passenger footwell area…that is why you see dashed lines around it and the run/crank relay…not in the back.
I think moisture may have got into your Tail Lights or side lights, maybe pop them out and give them a good inspection, look inside them if you can.
Does it happen after hitting Bump? You know what I'm getting at.
Have you noticed similar things when it happens or how often?
I'm guessing but the car wash thing has me leaning to the issue, also inspect the side markers inside and out.
I think water got into one of the exterior lights.
Sorry forgot to include the year. Its a 2013 c6 GS. Electrical is very intimidating for me so I have no clue where I would find the ground for this.
I feel like its a moisture issue as well...I wash on my own at the overhead car washes with the pressure washers. I've been avoiding the lights with the pressure washer. Not sure how it will ever be able to be avoided if it's a moisture issue.
For the BCM I meant the back side of the module under the passenger side. I can't figure out how people are getting to the relay on the back of this thing. I was thinking I just had to remove the bolt that's in the red section of the module and that's the "back" but that's not it!
First off wash the car yourself and never at a car wash !!…that is a Corvette Cardinal Sin !!…those things will scratch the hell out of your paint…there are 3 bolts that hold down the BCM…see below…first disconnect the negative battery terminal and the 2 blue connectors are lever lock…a bolt holds the last connector in place…just unscrew the bolt and remove it…I have a feeling you are not very mechanically inclined and if your capability is not beyond changing a fuse I suggest taking your car to an auto electrical shop for a diagnosis.
Thanks, I was hoping it didn't have to be the whole unit, just felt excessive for a relay!
Thinking it's a moisture issue and not a relay issue now. Tail lights have been working again for a week now and then this morning the headlights were fogged up with condensation & the tail lights would start and stop working on my drive.
Any ideas on how to avoid moisture affecting the lights?
For your Tail Lights there is a Vendor in here, I will have to see if I have saved Link when I'm home that sells a gasket you put around tail lights that stops water from going behind them, I have them on mine.
As far as headlights some of the more seasoned guys may be able to chime in and help better than me.
But my thoughts are without baking the lens off to create a new seal around housing and lens, I would think maybe use some Clear Silicon Caulk as a half *** fix. Without looking at where lens meets housing the ideal would be beyond bumper/Fender so not to see Caulking.
Its that or buy new lights or re-bake them.
If it were me I would Buy new Headlights. Just my humble opinion
I was going to buy those tail light seals off Vette Lights and hope for the best!
Was also going to try dielectric grease on the connectors to try to prevent any moisture from getting inside. (Recommended by ChatGPT so let me know if you guys think that's a horrible idea haha!)
I had a similar issue with my 2012 Grand Sport. Turned-out to be a faulty ground wire inside of the tail harness connector itself. I posted about it 13 Nov 21 titled "Frustrating electrical issue (long read)". I included photos of how I solved the issue - hopefully, this might be of help to you. I finally made a bypass wire for the connector - which worked great. It was a pain to trace-down, but ultimately cost me no money to solve.
Here's a description of my problem: "2012 Grand Sport under 20k miles, all stock lights (no led's). I have an electrical issues at the back of the car. So, I noticed while driving, that both the left and right blinkers were hyper-flashing. So I pulled into a parking lot to investigate (it was during the evening). I then discovered that none of my lights at the rear of the car were working (all of the front lights were functioning fine). This means that none of the following were working: (1) tail lights, (2) rear side markers, (3) brake lights - to include 3rd brake light, (4) reverse lights, and (5) license plate lights. Not wanting an accident to happen because of the no tail lights situation, I asked a friend to follow me home. Half-way to my house, he texts me to say that my tail lights, brake lights and turn signals had suddenly started to function again. So, he followed me for another mile or so, then turned around to go home. My lights seemed to work just fine for the remainder of the trip, until I turned into my gravel driveway (which is long and bumpy). They quit working like before and still do not work (while in my garage). After parking the car in the garage, the things that I've determined to work at the rear of the car were: (1) NPP exhaust valves (stock, without an aftermarket controller), (2) gas door lid via button activation from the dash, (3) rear hatch opening using the fob, the button on the dash and the button above the license plate, (4) the rear hatch latch draw-down mechanism, and (5) my backup camera (aftermarket stereo head, stock Bose speakers). Things I checked: EVERY mini-fuse I could get my hands on, both in the passenger footwell (I discovered two additional smaller, covered fuse blocks along with the obvious, large un-covered main interior fuse block), as well as the fuse block in the engine compartment. I didn't just remove and look at these fuses.... I used a meter to verify each one of them individually (set to ohm with sound - beeeeep!). I didn't want my eyes to fool me. NONE of the mini-fuses were blown. I removed all four of the tail light lens assemblies from the car in order to inspect the wire harness back there. Anything looking like a grounding stud and whatever wires was attached looked to be solid and corrosion-free. There was also a braided grounding strap that looks properly connected and corrosion-free. I don't mind putting in the effort and using a meter to wring out wires and components....I'm just at a loss on how to logically proceed. I wish to completely avoid taking my car to the local dealership for this. I feel that I can't be the first one with this sort of problem. I've read on this forum where somebody had a very similar issue, but it was because they had a trailer wiring harness that was grounding-out and blowing fuses. I don't have any of that going on back there. If there's something I'm missing, I'll be happy to proceed and post results in the interest of maybe helping somebody else out with this issue.....if it's constructive in nature. I've done an internet search and also searched YouTube, which was mostly time wasted (all the typical title of video not matching the content of the video, and other suggested videos and crap that had nothing to do with my issue)."
Hopefully you can access that thread and hope it proves to be helpful to you. Good luck!
I'd start with the easiest things first. Check all the connections that you changed, touched, or might have touched. Make sure they're all snug and secure. Especially grounds. As well make sure you have absolutely perfect grounds.
Yup, look here. Maybe a bit of di-electric grease on the ground connections....
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Intermittent Rear Light Failure
