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Go Back   TDIClub Forums > TDI Model Specific Discussions Areas > VW Passat Family (NMS and B7) TDIs (2012+)

VW Passat Family (NMS and B7) TDIs (2012+) Discussion area for the 2012+ Passat TDI (North American and rest of world versions versions). The North American model was previously codenamed NMS (New Midsize Sedan) and the version the rest of the world gets is sometimes referred to as B7.

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Old July 5th, 2013, 07:49   #1
copbait
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Default Electrical question. Brake lights stay on all the time

I have run into another problem. Now that the motor is back in and everything is working correctly except the brake lights stay on all the time. I ran measuring blocks and it shows the module think the brakes switch is on, so I unhooked the connector to the brake switch and it now shows off but the brake light stay on.

So do I replace the brake light switch, or is there a problem with the module?

I also noticed in the measuring blocks there is a block for brake light switch via CAN which shows not connected, this is not applicable on the MNS Passat is it?
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Old July 5th, 2013, 08:02   #2
compu_85
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Our cars don't have a CAN brake light switch. I'd guess the lights being on is a fail safe. I don't know if the switch is adjustable, it was on older cars... perhaps something got tweaked in the accident?


-J
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Originally Posted by BRUSSELS BELGIAN View Post
Maybe I should pay MYSELF to do bad work on my car!
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Old July 5th, 2013, 10:25   #3
copbait
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I didn't think by the look of the wiring diagrams that the brake switch was CAN, thanks for confirming!

I looked at my parts clip and found another electrical system control module, so I installed it, no change. I like throwing parts at it when it does not cost any money

Don't know where to go next
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Old July 5th, 2013, 10:42   #4
compu_85
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Does your parts clip have foglights? If so I'd be interested in buying that control module from you

-J
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2012 Passat SE TDI DSG. 60,000 miles. Factory Alarm, LED tails, Memory Seat, HIDs 38/48 MPG.
99.5 Jetta "GLX" TDI. 295,000 miles. Half way there!!! Power Memory Seats, HIDs 11mm pump, BV39 Turbo, RCIII 36/47 MPG.
1991 Mercedes 350SDL 230,000 miles, 70,000 on engine. 18/27 MPG.
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1988 Audi 5000S Quattro, 1992 Jetta ECOdiesel, 1991 Jetta ECOdiesel.

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Originally Posted by BRUSSELS BELGIAN View Post
Maybe I should pay MYSELF to do bad work on my car!
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Old July 5th, 2013, 13:11   #5
VeeDubTDI
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Is it possible that the brake lights being on is due to deployed airbags? Safety feature?
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Old July 5th, 2013, 13:16   #6
copbait
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It did have foglights, let me see if I can find a module for it. I have found the kessy module and one other one, not sure what it is for.

VeeDubTDI- that is what I thought also but I have cleared all crash codes, the only codes left are high resistance codes from the seat belts being out.
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Old July 5th, 2013, 13:17   #7
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You're one step ahead of me, then! I'm out of ideas.
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Old July 5th, 2013, 14:56   #8
copbait
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compu 85 - It looks to me the fog lights get there power through the electric system control module, it that what you need, I also have the headlight switch.

VeeDubTDI - Thanks for the brainstorming. Do you know how the transistor style brake switch works. I was wondering if maybe just removing the positive input (unplugging the sensor) is not enough to shut off the lights, maybe it would need a negative input to turn off the brakes. My only thought before I take it to the dealership is to try replacing the brake switch
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Old July 5th, 2013, 15:01   #9
VernK
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Looking at the wiring diagram, I see that the ABS module has a terminal that is connected to the same terminal as the brake light switch on the electrical system control module. Perhaps the ABS module is bad. See if terminal T47/38 (should be black with red wire) on the ABS module is +12V with the key on and brake switch disconnected. If it is that is probably the fault.

That's the only connection I see, but then I'm still learning to read VW diagrams.

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Old July 5th, 2013, 17:34   #10
copbait
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Well VernK, I did you one better, I back probed the wire running between the Brake Light switch and the module. There is a consistent B+ there with the ignition on and the switch plugged in, it is neutral with the switch unplugged. Then I back probed the wire leading from the module to the high mount brake light, and with the ignition on there is a consistent B+ at the wire and at the pin of the module. So I am left to the conclusion that either the switch needs to send a ground signal with the brakes released or there is a fault code somewhere I can't find but I have run Autoscan on VCDS so I can't imagine that.
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Old August 9th, 2013, 17:19   #11
copbait
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I got it. I think what happened is the man that wrecked the car had his foot on the brake when he wrecked, and when the engine came lose the turbo hit the booster and master cylinder and jammed the piston in a semi engaged position.

Anyway I noticed the brake booster was crushed and decided to order a new booster and master cylinder and that fixed my problem.
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Old August 9th, 2013, 20:31   #12
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So the electrical system was working perfectly. Brilliant that you've got it sorted.

Yours
Vern
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