Lights Won't Turn Off - Headlight, Tail Light, Licence Plate Light

I was doing some work on the trailer wiring on the car and when I was done I noticed the car lights were stuck in the on setting. I also swapped the the interior dome lights and the trunk light to LEDs before I noticed the issue.

• Tail Lights
• Headlights
• Licence Plate Lights
• Interior Illumination Lights (lights behind all the controls)

Are all on and stay on regardless of the headlight switch position. They do all go off when the car is off but remain on if the car is on.

On the trailer wiring all I did was cut the stop(Brake) wire from the powered curt controller to get my brake lights to work on the trailer. Which they do now.

My aftermarket back up camera wiring was also loose so I reconnected that to the back up light wire with a T-tap connector. I also wired a OBD II port connector to my kenwood headunit for the gauges leads.

I looked at the headlight fuse under the hood and it seemed fine. Its a 30 amp whereas the manual states it should be a 40 amp. Also when I removed the fuse only the driver side headlight went out every thing else remained on.

I removed the headlight switch and that made no difference as well. Since I was doing so many wiring repairs I'm not sure which spot of the car I might have messed something up. Or if it's just a coincidence and the problem is unrelated.

Anybody have any other ideas?

Only thing I can think of is I had an MK6 that I had put HIDs on and it fried the BCM which didn’t ever work properly again. It would leave the lights on, only turn on one brake light, etc.... The only other thing is that have done LEDs on many cars and they can cause weird electrical gremlins, especially when replaced en masse. Maybe the computer thinks they’re off and leaves them on due to the low voltage usage? Double check your BCM and report back!

How can I diagnose the BCM to confirm if it is the culprit or not?

I guess this is why they tell you to always remove the negative battery terminal before doing electrical work on your car.

OBD works, start there. See what the Central Electronics Module is reporting for DTCs, if any.

You really need to watch what you do with these cars. The lighting is not always as simple as you may think it is. This leads to call kinds of crazy stuff happening. All of the lighting goes through the CE module. There are no separate tail/brake/turn bulbs, they are all the same bulbs, the CE controls which one and how much voltage is applied (based on the inputs from the various switches) to make them do what they are supposed to do.

This is why the proper VAG Control Unit for Trailer is so important. Because it communicates on the CAN bus just like all the other modules, and it receives the proper signals to work the trailer lights (among other things) without having to hack into the car's wiring.

1K0-907-383-F

I only have a generic scanner so not sure if it will pull up any codes but I will try it.

I also noticed I am unable to turn the lights on at all if the key is not in the on position. So at least I won't have the issue of forgetting to turn the lights off.

Maybe I can try replacing some the the LED bulbs with the originals and see if that makes a difference.

Your generic scanner is useless. It is really advisable to get a proper scan tool if you are going to do much of anything yourself to one of these cars. It is akin to a Phillips screwdriver in 1970.

Do your headlights and other lights switch on and off correctly. other than staying on?
Agreed, a generic scanner will not pinpoint issues. There might be someone near you with a VAGCOM you can borrow. Sometimes people post on Craigslist that they have one and can help you scan codes.

If your lights turn on and off correctly, ie you turn on the headlights and they go on, brights go on and off correctly, brake lights work when pedal is depressed, etc, your BCM might not be the culprit. If you have no way of getting a scanner, you might want to go back to all your old bulbs and see if that changes anything. LEDs can cause weird gremlins. That would be time consuming so plan accordingly.

Best of luck!

I remembered that I had my friends VAG401 Xtool scanner that I used to prime the fuel filter when I changed it last. So I thought I would give that a shot.

I went to scan the car only to realize the scanner would not power on. My ELM327 scanner would not turn on either but my OBD fed gauges on the head-unit would work. So I knew the data was transmitting but the scanners were just not getting power. It turned out to be a blown fuse. #13, 10 amp fuse in the driver side panel.

So after I changed the fuse and I scanned the car with the Xtool. It came up with an 01304 error (Radio Open Circuit). I cleared the code and the issue went away.