Golf Mk5 1.6 fsi 2004 Brake lights on when ignition on and working normally ignition off ??

[Columbusracing]

2004 Golf Mk5 1.6 FSI BAG engine

Cruise control inoperable and the brake lights illuminate and stay on constantly when the ignition is turned on when the ignition is off brake light works as it should when engine is running.
Had the following code:

16955 - cruise control brake switch A

I have swapped the brake light switch with a replacement which made no difference. Must be a short somewhere due to the power to the brake lights when ignition is off.

Anyone any ideas or experiences?

Seen another similar thread with no solution anyone got any ideas

[owler]

It sounds like the switch as I had a similar fault and code 16955 showed up on diagnostic test. Thinking about why the switch has two sets of contacts it makes sense that one side is for the cruise control while the other is for brake lights.
The new switch has rectified all faults but there are multiple switches so make sure it is the correct one for your car.

[Crasher]

Are the lights on if you unplug the harness from the switch?

[Columbusracing]

sorry for the late reply didn't ever turn the ignition on with the switch off so not sure but will have to ask my mate to try it. Thats a good idea though would point to whether theres just a direct short making the switch redundant.
cheers

[Columbusracing]

Little update have tried with the switch unplugged but makes no difference brake lights are on with ignition. With the ignition on the lights are on - removing all the fuses from the fascia fuse box the only one to effect the brake lights is to remove the fuse 29 engine management.

I can shut them off removing a couple of fuses from the engine bay fuse box aswell.
Fuse 16 - Steering Column Control Function
Fuse 26 - engine management
Fuse 40 - Fascia Fuse board

Does anyone know if the multifunction unit that control the rear lights has a connection to the engine ecm?
The multifunction unit for the brake lights has a number of relays on but i cannot find anything to tell what they are.

Are multifunction units common on these?

Cheers

[Crasher]

The brake lights are individually powered from the "J519 Onboard supply control unit" from two different multi-plugs so the problem lies within the J519, either it is faulty or is being commanded to turn on the brake lights. You need to observe the J519’s switch inputs in Measuring Blocks 08 using a diagnostic computer. You don’t mention fuse 14 extinguishing them so that rules out the input to the pedal switch. In the absence of a diagnostic computer, I would check for ignition on power at the black/red wire on the brake light switch plug when it is unplugged from the switch. If it does have power, take out the dash side fuses one by one and see if the power goes and also try the engine bay fuses again. Removing these fuses will cause fault codes that will have to be cleared.

[Columbusracing]

Well the car has lost 5/6 th gears aswell which is nice and my mate who owns it has gotten a train home so i have a little time to play with it. Will have to see what options i have with my diag gear don't have vcds at the moment but should have something to check it with.

Will check for 12v on the brake switch terminals if there is 12v with the fuse out on either terminal then maybe a short in the circuit feeding the J519.

Gonna have to pull the box out and send it for repair seems to have a selector shaft problem all the linkage moves as it should but gearbox doesn't select gears in the fifth or six position. I even pulled out the linkage on the box and moved the selector which the linkage should have been actuating and still no gear selected.

[trs888]

i came back to the car to find my brake lights on when it was locked. happened twice, so i contacted my VW mate, he said probably the J519 unit. he had a similar thing on an R32 earlier in the week.

he suggested disconnecting it for up to 15 mins, and then plugging it back in. does a kind of reset.

might work for you, i havent tried as yet due to bad weather!

worth a shot tho!

[Columbusracing]

Finally got the golf out again to play with today and want to get the brake lights sorted before taking the box out so got my new vag com out and had a little play.
Ignition off brake switch operates normally -09 central electronics - brake switch open 1% brake switch closed 100%.
Turn on ignition and brake switch stays 100% if you go into engine with ignition on its 100% aswell manipulating switch makes no difference. Checked the voltages with my power probe all good switch operates as it should.
Tried pulling fuses again and relays with the multifunction fuses and control relay removed brake lights still on. As i've said before only engine management fuses turn them off. Fuse 29 in fascia.
So i have been through all the diagrams i can get hold of seeing what effects the multifunction from ecm side only brake switch by the looks of things.
Checked fuses again and i can disable the brake lights by removing maxi fuse 48 in the engine fuse box. What i really need is a multifunction wiring diagram as i still have no idea which pins do what on the unit and for some reason none of the plugs from it want to disconnect.
Gonna have a search in a minute for a how to on removal/replacement of j519.

Any input greatly appreciated

[Crasher]

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