Wangfap

Hi everyone, I recently joined the Audi family with a 2007 A4 2.0T.

I noticed the other day the cruise control wouldn't turn on. After a little research, I initially thought clutch switch. But then after I took it out at night I noticed the brake lights were stuck on, so I decided it was probably the brake switch and ordered one (1K2 945 511 RDW). Other than the brake lights being on (and that causing the cruise control to not function), I have no errors or lights on the dash.

So this morning I decide I'm gonna check out where the sensor is and how it's put together before the new one gets here. I disconnected the connector from it and tried turning the ignition to On and the brake lights were still on. I didn't mess with the plunger for fear of accidentally pushing it all the way in or something. Put everything back together, the brake lights still function normally when the key is off or out.

Now I'm thinking the new switch won't help anything. There were a couple people with the same issue posting in an old thread that I found here: Brake lights are stuck on - Help! - AudiWorld Forums but to no avail.

Another possibility that I'm thinking of is a fuse in the box in the engine bay, but there's one screw I can't access at the moment (I ordered a set of torx wrenches from Amazon that should be able to squeeze in there) but from what I've seen, people with that issue also had other errors/lights on the dash.

Finally, I ordered a genuine cable from Ross-Tech, but have no experience with VCDS. I'm hoping that at the very least that can help me track down this little problem (and turn off the annoying beeps and chimes!)

Anyone that had this problem and was able to fix it or that might know of something else that I missed in my searching, your help would be greatly appreciated.

Wangfap

So I got my VAG-COM cable in today, hooked it up and found 2 codes.

Brake Switch: Implausible Signal

ABS Control Module: Intermittent communication

Now I'm feeling a little better about it maybe being the brake switch (which should be here tomorrow).

John535is

When you get the new switch:
1. DO NOT play with it!
2. Still DO NOT be tempted to push the little plunger in to test it. why - These switches have a self setting ratcheting mechanism inside, once you push the little plunger in, it will not come back out more than a fraction.
3. Installing them is easy as long as you have been doing your advanced yoga and kept up your contortionist lessons, otherwise a bit of swearing and a lot of stretching is involved. To remove the old switch, unplug the wiring and turn 90 degrees, it pops out. (no tools).
5. Now be careful when installing the new switch the pedal is up as high as possible, install the new switch, plug in, then carefully check the alignment of the plastic plunger is behind the pedal and aligned straight. If it does not align straight is can snap off. When you push the pedal down, the switch will self level and only return a fraction.
Then you're good to go.

I know this sounds straight forward but I have seen people play with a brand new switch and push it in, then realise they have to buy another, and I have seen an Audi apprentice break one installing them, so just be carefull and its straight forward.

Wangfap

Thank you for the information! Success!! I realize now how the circuit works and why removing the connector from the old switch as a test didn't work. Brake lights function normally all the time now, and cruise control is working.

Vilius Pocius

Can you explain how it works?