Electrical question. Brake lights stay on all the time

copbait

Veteran Member
Joined
Oct 16, 2010
Location
Johnson City TN
TDI
97 Passat TDi, 13 Passat TDi SEL
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?
 

compu_85

Gadget Guy
Joined
Sep 29, 2003
Location
La Conner, WA
TDI
... None :S
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
 

copbait

Veteran Member
Joined
Oct 16, 2010
Location
Johnson City TN
TDI
97 Passat TDi, 13 Passat TDi SEL
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
 

compu_85

Gadget Guy
Joined
Sep 29, 2003
Location
La Conner, WA
TDI
... None :S
Does your parts clip have foglights? If so I'd be interested in buying that control module from you :)

-J
 

VeeDubTDI

Wanderluster, Traveler, TDIClub Enthusiast
Joined
Jul 2, 2000
Location
Springfield, VA
TDI
‘18 Tesla Model 3D+, ‘14 Cadillac ELR, ‘13 Fiat 500e
Is it possible that the brake lights being on is due to deployed airbags? Safety feature?
 

copbait

Veteran Member
Joined
Oct 16, 2010
Location
Johnson City TN
TDI
97 Passat TDi, 13 Passat TDi SEL
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.
 

VeeDubTDI

Wanderluster, Traveler, TDIClub Enthusiast
Joined
Jul 2, 2000
Location
Springfield, VA
TDI
‘18 Tesla Model 3D+, ‘14 Cadillac ELR, ‘13 Fiat 500e
You're one step ahead of me, then! I'm out of ideas. :eek:
 

copbait

Veteran Member
Joined
Oct 16, 2010
Location
Johnson City TN
TDI
97 Passat TDi, 13 Passat TDi SEL
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
 

VernK

Veteran Member
Joined
Jul 31, 2012
Location
Kelowna
TDI
2012 Passat 2.5L Gas
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.

Yours
Vern
 

copbait

Veteran Member
Joined
Oct 16, 2010
Location
Johnson City TN
TDI
97 Passat TDi, 13 Passat TDi SEL
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.
 

copbait

Veteran Member
Joined
Oct 16, 2010
Location
Johnson City TN
TDI
97 Passat TDi, 13 Passat TDi SEL
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.
 

VernK

Veteran Member
Joined
Jul 31, 2012
Location
Kelowna
TDI
2012 Passat 2.5L Gas
So the electrical system was working perfectly. Brilliant that you've got it sorted.

Yours
Vern
 

Anis7867

New member
Joined
Oct 7, 2019
Location
Stoke
TDI
Passat
Breaks light stay on!!

Hi guys I was wondering if someone could advise me on a issue I have with my passat 2012 1.6 Tdi Estate.. the break lights are always on when you put the ignition on... after a diagnostics it was saying there was a issue with the break switch we replaced the switch and nothing.. we even removed the switch and the break lights stay on.. however when we take out the ignition relay the breaks work as normal ??*♂...(but obviously I cannot start the car)
We tried a used body control module and still nothing... rewired it from the switch and still nothing... I did have a issue with the battery before this all happened.. The car came up soo many faults but changing the battery put everything back to normal.. I was wondering could this have triggered a default setting on the break lights? (I did purrchase a genuine agm battery)
 
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