dustboy

On to the next problem, we had the ABS and Traction lights on for several months. Little did I know that the rear brake lights were also not working. My mechanic changed the brake light switch, and everything worked again. Easy, right? Nope.

So now the dash lights went on again and the brake lights (all 3) aren't working, mechanic changed the switch again and this time it didn't fix the problem. This second time, it may have coincided (wife is unclear on this) with the car stalling on the highway and requiring a $750 tow.

There are no OBD-II codes. Weird problems like this make me think of a bad ground, but I wouldn't know where to start with that.

Any ideas?

amiram

Chinese brake light switch?

dustboy

I guess it's possible we got two bad switches, but my mechanic is very picky about using OE parts. He has been working on VW's for 30 years.

About the same time that the ABS lights came on, I had disconnected the ride height control module underneath the rear cargo area. I guess I'll try plugging that back in, maybe it's causing issues with the BCM.

Another idea I just had is that maybe there's a short in the harness to the tailgate, in that case, the BCM probably shuts off that circuit. When the car is first started, the ABS light is off until the second or third press of the brake pedal.

dustboy

Just ordered a VAG-COM scanner, I would have gone with the Ross-tech setup but I don't have a PC running Windows 7.

I hate to second-guess my mechanic but he did mention that he is using a Snap-On scanner that doesn't read the VAG-COM codes. Hoping that if there is in fact a second bad switch that this scanner will show that.

dustboy

Got my VAG-COM scanner (best $35 I ever spent) and sure enough, it shows a faulty brake light switch. Cleared the code, tapped the brake 3 times and the code came right back.

For grins I pulled the engine codes...Yikes, there are about 3 sensors that appear to be failing, but apparently not enough to throw a MIL. When I scan with my generic OBD-II it comes up all clear.

John535is

methinks your very picky mechanic who has worked on VW for 30 years but is only using a snap on generic OBD2 scanner may not be what he claims! ( I bet he charges like a specialist!). You might want to think of trying someone else.

The brake light switch is a DIY. I recall a genuine one is only $25.
check part #1k2945511rdw. for post 2002 models.

There is only two 'tricks'.
1. Don't play with it!. I'm serious, the switch will self set to the correct distance, so if play with the new switch and push the plunger in, it won't come back out, so leave it fully extended and let the pedal push it to the correct level.
2. the plunger is plastic and can snap. make sure you don't try and twist the plunger, push the brake pedal up as far as it will go, there is enough clearance.

From memory, you don't need any tools, just twist the old one 90 degrees and it comes out, electrical plug on the back.

dustboy

Well, you are mostly right about my mechanic, we've stayed with him because he is very honest and reasonable. Since he couldn't fix the brake light issue he didn't even charge us for his time or even the new switch, and his hourly rate is half what anyone else charges. But yes, he is very old school, he would really prefer not to work on anything water-cooled.

I dug into the issue myself, and bought a switch at the local auto parts shop (not OE). Same result, however the shift lock solenoid did release when the brake pedal was pressed. Checked the harness at the switch, no voltage. Checked the fuse, it was blown. It had been replaced by the mechanic previously, and it blew again when I replaced it. My wife said she saw the center brake light and right brake light flash, but not the left, so I suspect the short is in that branch of the wiring.

I replaced the fuse a second time, and (knock on wood) it has not blown yet. Cleared the codes, and everything is working properly, we drove it for a couple hours yesterday and the problem did not reoccur.

What I learned about the brake switch:
1. I disassembled the switch to see what is going on in there. If it fails, it is because the plastic mechanism insided has broken, or it was installed improperly.
2. The installation is actually very simple: insert the plunger through the bracket until the switch seats in the bracket, then twist it clockwise to lock and set the correct plunger length. No need to fiddle with the pedal, the switch should be set to the pedal's resting position. You can play with the plunger without doing any harm, this may be a newer version of the switch than one that was a one-shot setup. I have both the VW and aftermarket switches which are identical except one lacks a "VW" logo.
3. The switch is not permanently set when you install it, it can be removed and reinstalled without damage. The calibration mechanism releases when it is turned counter-clockwise and removed from the bracket, and the plunger returns to its full length.
4. The switch contains two switches. One controls the shift lock and the other controls the brake lights.

alvocado

Has it been confirmed that the switches can be reset and are not one-time adjustment? I just installed a new OEM switch to replace a lazy brake switch and am getting ABS/ESP lights and unable to shift the transmission out of park. I followed the factory service procedure: install switch, depress brake pedal and rotate switch 45 degs, attach wire. I removed the new part and reinstalled the old switch and that is also throwing the ABS/ESP error. Has anyone successfully removed and reused one of these switches?