Tail and backup light puzzle

[PlaidDad]

My ‘17 Rs lighting is acting odd. Both tailgate parking lights are out, plus the passenger backup light. The bulbs are all new, I cleaned the contacts on the bad backup light and have continuity between them on the lamp holder with a new bulb. The owners manual doesn’t ID a fuse that would just cover these, the one it implies would be in question covers other stuff that is still working.

Suggestions? I’d start by checking voltage on the connectors, but don’t know which pins to check.

 

[mr-fix]

Any bulb related messages on the displays?
Any mods with OBDeleven/VCDS?

 

[PlaidDad]

Error messages on the individual bulbs that are out. No mods.

 

[Michael gti07]

Reset the bulb out code. With a helper in a shaded area, see if lights flash the lights when you turn the car on. Check the functions with your helper.
Sometimes the cold check is persistent. This is the behavior I see when the car doesn't like new leds in incandescent housings, so it may be the computer holding onto old data.

Just check the fuse box for burned fuses. Both engine bay and under the steering column.
If you have a fuse continuity checker, it's faster than a flashlight. I think all the new fuses now have the 2 check points on top.

 

[DV52]

@PlaidDad : Don't bother searching for a fuse for the tail-light lamps - you won't find any!!

On MQB platform cars (like the mk7/mk7.5), protection of the car's 35 x exterior lamps is managed by the module that lives at CAN address hex09 (it's called "BCM" by VCDS & "central electrics module" by OBD11). This module is very sophisticated (see the motherboard below) and it continuously monitors each lamp separately - and if it detects a problem, it will both limit the quantity of electrical current that is injected into the fault and it will generate the error message that you have observed!

So - what is the cause of your errors? I'm not sure but if "Both tailgate parking lights are out" - it's a strange problem because the rear fittings on each side of the car are controlled by different wiring looms and by different pins on the BCM!

If this was my car, I would be looking at what might be the common element for the two lamps on either side of the car. Maybe a good starting point might be to examine the earthing for the fittings which on RoW models is the brown wire on pin #2 on each side? I don't know if your NAR model cars use the same wire color (I don't see many American cars down here in the very deep south )

Don

 

[PlaidDad]

Thanks, will check the grounding. Bulbs are not LED, and I’ve confirmed they are in fact out.

appreciate the feedback.