No brake lights - Brake light switch, bulbs appear to be fine?

[computiNATEor]

Hey folks,

In another episode of "what's wrong with my E39", I was picking up some Krispy Kreme doughnuts and coffee in my E39 today, and when I was on my way back home, I got a "check brake lights" error. Hmm, must have a bulb out. Nope. After filming the back of my car while I pressed the brake pedal, I had ZERO brake lights working. Hmmmm.

So I grab my laptop, scan the LCM with INPA, and see that the brake light switch is working properly through the "read status" page. BMW Scanner 1.4 agreed. However, the live data from the LCM claims the all the brake light bulbs are out. Center, and both tail light brake lights. What are the odds of that?

So the brake light switch is working, or at least the LCM thinks it is. The taillight brake light bulbs were swapped with the reverse lights; they're working. The center taillight bulb was suspect, so I changed it; it's working now.

All of the other bulbs in the car are working - indicators, Celis taillights, reverse lights, all working. The outer brake lights - the most important lights, IMO - aren't working. Still getting a "check brake lights" error message. I changed the bulbs with some from my box of spares - still not working. I cleaned the contacts in the taillight connectors with CRC QD contact cleaner. No dice.

Has any one else experienced a problem like this?

I need this problem fixed, obviously. Sooner the better.

- - - Updated - - -

Checked fuses, obv. Swapped fuse 41 (brake lights) and 43 (same amperage); no difference.

[computiNATEor]

Ok, well, this is a new one. It would appear that the taillight socket in the taillight housing was not making good contact with the "wiring" in the taillight. When I removed the taillight, there is a very slight amount of corrosion inside the socket housing. Like, really light corrosion. Now I have left and center brake lights. I will take photos of the right taillight before I fix it, if indeed that is the issue.

- - - Updated - - -

Also spent about an hour getting the WDS to work again. Grr.

[Jason5driver]

Ok, well, this is a new one. It would appear that the taillight socket in the taillight housing was not making good contact with the "wiring" in the taillight. When I removed the taillight, there is a very slight amount of corrosion inside the socket housing. Like, really light corrosion. Now I have left and center brake lights. I will take photos of the right taillight before I fix it, if indeed that is the issue.

- - - Updated - - -

Also spent about an hour getting the WDS to work again. Grr.

Mine did that as well.
The gasket seal dries up and doesn't seal anymore, letting in water.
Mine were so bad that it heated up the bulbs and melted the plastic, so I had to replace them.

[computiNATEor]

Mine did that as well.
The gasket seal dries up and doesn't seal anymore, letting in water.
Mine were so bad that it heated up the bulbs and melted the plastic, so I had to replace them.

The taillight gaskets were not well made in these cars, it would seem. I installed a new right taillight (one of the mounting screws was broken) that I had lying around; I can install a new left taillight soon. I also have new gaskets.

[computiNATEor]

Here's the level of corrosion that stopped both rear brake lights from working at the exact same time (AFAIK).

Left taillight, after being cleaned up with a brass wire brush, and before being cleaned with some vinegar on a q-tip:
1 Left.jpg

Right taillight, before any cleaning. I replaced it due to previous water ingress in taillight, and not at all because I had a spare lying around:
2 Right.jpg

I also cleaned up the socket contact points with the brass brush, and I replaced all three brake light bulbs with new ones.

My expensive SilverVision turn signal bulbs are still going strong, and the car is back to its normal, error free dash.

[philly98540]

Glad you solved it. Those gaskets on the tails are marginal at best.

[geargrinder]

Hey Nate - strongly suggest you give those surfaces a squirt or wipe w/ a contact 'cleaner' / lube like Deoxit after you cleaned 'em up. If there's any residual vinegar acid left there it'll be super corrosive over the long term... Some product like that should neutralize that, and then provide a bit of surface coating to prevent more corrosion. Use a little WD-40 if you have nothing better (can replicate the Q-tip application so you don't spray oily crap into the lens itself).

I'm guessing there's something about using a common ground for diagnosis or something that made the bad reading on one side take out both sides 'logically'. There's a lotta advantages to modern LCM type module control - basically they eliminate the need for a lot of extra specific fuses and can identify bad bulbs etc - but once in a while they cause something funny like this where an old-timer switched brakelight would have kept working fine.

[computiNATEor]

Hey Nate - strongly suggest you give those surfaces a squirt or wipe w/ a contact 'cleaner' / lube like Deoxit after you cleaned 'em up. If there's any residual vinegar acid left there it'll be super corrosive over the long term... Some product like that should neutralize that, and then provide a bit of surface coating to prevent more corrosion. Use a little WD-40 if you have nothing better (can replicate the Q-tip application so you don't spray oily crap into the lens itself).

I'm guessing there's something about using a common ground for diagnosis or something that made the bad reading on one side take out both sides 'logically'. There's a lotta advantages to modern LCM type module control - basically they eliminate the need for a lot of extra specific fuses and can identify bad bulbs etc - but once in a while they cause something funny like this where an old-timer switched brakelight would have kept working fine.

I did; CRC QD contact cleaner was liberally applied (to a q-tip and directly into the connector).

That makes sense, actually. However, I've had similar (worse) grounding and rust issues in the past (I had an internally cracked taillight in my first E39 which allowed water in), but with just one bad bulb.