Brake lights, rear lights, and "!"

Hi.

I have lived with those warninglights for quite a while, but today I felt brave enough to deal with them.

I changed all the lightbulbs in the rear to get the same manufactor (GE Electronics.)

The warninglights is still on... and now I can't shut of the "!"-sign.
All warninglights are functional, so there must be something strange going on.
I did find a tiny black VDO-box under the glove-compartment, mounted to the shelf. On the box I could read something about the rear lights and brake lights and the central warning unit. What is this thing? I opened the box and found one dead capacitor on the cirquit board. I replaced it and resoldered everything. Still no change.

What can it be?? I don't feel very happy at the moment. For every problem I solve, two or three new ones occur. I have gone through every ground point I've found. Every fuse, every socket, every blabla and so on.

 

It is the lamp control unit part of the taillight monitoring system .

 

Can it "freeze" the "!" sign?

First came the Schluss-warning, then came Bremslicht about 1 month after.But I have always been able to shut down the light...

 

I found another VDO-box inside the center console below the stereo. What is that for?

 

Clean the bulb sockets - it only takes a bit of dry powdery corrosion to alter the measured resistance and trigger the warning.
jp 83 Euro S AT 48k