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MFD says rear right brake light not working....but it is!

T

Tip-C

Ready to race!
Location
Montreal, Canada
Weird problem...

When I turn on my car, the MFD shows be that my rear right brake light isn't working and that little yellow bulb light is on when i drive.

Curiously, i checked in the back of the car and both my rear lights are working properly...When i press the brake both light up!

I don't get it...What could be wrong? and what can be done to get rid of this message if nothing is wrong? VagCom maybe?

PS: no dealer...The car's warranty is expired due to millage.
 
9Schnell

9Schnell

Euro-Elitist
Location
Seattle
Car(s)
2010 CC Lux
Both light up or all 4?
-theres 2 on each side.
 
T

Tip-C

Ready to race!
Location
Montreal, Canada
9Schnell said:
Both light up or all 4?
-theres 2 on each side.
Click to expand...

Not my car or picture...but it lights up just like this:

 
mike1947

mike1947

Old Man
Location
San Luis Obispo, Ca
MFD says light bulb out

Same thing happened to me; it turned out to be a warning that the light was about to go out. It did burn out within a week. I think it's a feature.
 
9Schnell

9Schnell

Euro-Elitist
Location
Seattle
Car(s)
2010 CC Lux
mike1947 said:
Same thing happened to me; it turned out to be a warning that the light was about to go out. It did burn out within a week. I think it's a feature.
Click to expand...

Kinda, when the resistance is too large the computer assumes a light is out.

OP:
Take a look at the filiments in the lightbulbs at the rear and replace the bad ones :thumbsup: -could also be a bulb not seated correctly.
Then cycle the light switch and see of the message goes away...
 
Colt1522

Colt1522

Lucky so far
Location
Bay Area, CA
Car(s)
07 BLK GTI
Thats funny, just this morning mine did the same thing... also on the right. Both are fine. Taking it into the dealership next week for an oil change will get the deal with that then..
 
G

Graubart

Ready to race!
Location
Maine, USA
The computer is measuring the resistance of the two brake light bulbs and, if it detects a difference from spec, it says the bulb is out. The resistance can change and still have the bulb work. Buy a new bulb and try replacing each of the brake light bulbs in turn and testing. You will probably find one of the bulbs was out of spec.
 
UMassJ77

UMassJ77

JawnY
Location
Mass
Car(s)
MKV GTI DSG
dude when you hit the BRAKES only the OUTER RINGS will go BRIGHTER..you have a BRAKE LIGHT OUT!!! have someone stand behind the car or in the car and u stand behind have them hit the brakes, you will see...mine did the same thing. When you turn the lights on the rings/circles will light up, but it's when you brake that the outer ring won't go brighter.

so the MFD is detecting no current when you hit the brakes.
 
R

rtchow3000

New member
Location
livermore ca
VW rear brake light idiot light on dash

hello all, i have 2008 rabbit and 2012 jetta TDI; i had same problem on 2008 rabbit rear brake idiot light on dash. i changed out the left bulb but the dash light still on. checked all lights function, nothing. a policeman stopped my wife for her right brake light out. he was kind enough not writing a warning (fix-it) citation. i checked everything since this has been ongoing and the dash light stays on. i didn't want a fixed it warning ticket the next time she get stopped. there are two bulbs on each rear brake light assembly. after reading previous forum problems, i went ahead replaced all four bulbs since i do not know when were changed out with 78K. boom, the idiot light gone, happy day.:wub: i didn't have to reset the switch. anyone with jetta TDI problem please let me know before i dig into unwarrant spending. i love the TDI as uber driver getting 40-45 miles per gallon, saving on fuel expense.:thumbsup: in calif is $2.55 per gallon, highway robbery!:mad:
 
JetTurbo

JetTurbo

geezer
Location
South Florida, USA
Car(s)
2018 GTi Autobahn 6M
UMassJ77 said:
dude when you hit the BRAKES only the OUTER RINGS will go BRIGHTER..you have a BRAKE LIGHT OUT!!! ...
Click to expand...
Unlike 20th century cars that utilized dual filament bulbs to provide dual function running / brake light,
on modern Volkswagens , the same single filament bulb is used for both running lights and brake lights.
The Vehicle Electrical System Controller J519 (aka CEC) uses pulse width modulation
to dim the bulbs for running lights, and then provides full power for brake lights.
(Resulting in one less wire per side and a lower cost socket and lower cost bulb.)
Point is, if you have all four of the running lights, the bulb is unlikely the cause.
Intermittent shorts or open circuit, resistance issues, etc are a more likely cause.

OP Unless someone incorrectly changed a CEC setting, and
you do not mention any VAG-COM sessions in conjunction with the failure,
from what you describe, VAG-COM is not going to fix it
 
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