Brake light problem

[mmarcatili]

I have a 2012 Octavia RS. Recently my cruise control stopped working. I then noticed that my brake lights are always on when the car is running. I assume that the two problems are related and cruise control doesn't work because the computer sees the brake as being applied. I had the brake light switch replaced. It is mounted on the master cylinder on my car. After being without the car for 3 days and a fair bit of cost the problem is still there with the new switch. The mechanic had no idea what it might be other than to say it's an issue for an auto electrician. Spoke to an auto sparky who I must say didn't fill me with confidence that he could fix it without a bit of trial and error which would be at my further cost. Has anyone here experienced this issue and have some clues as to what it could be and how to check things and isolate the problem?

[kamold]

First thing you need to do is get the car scanned with a suitable diagnostics tool (eg VCDS, OBD11 etc).
The BCM (and possibly other modules) should have logged a fault which will be a good starting point for what the problem could be.

[mmarcatili]

First thing you need to do is get the car scanned with a suitable diagnostics tool (eg VCDS, OBD11 etc).
The BCM (and possibly other modules) should have logged a fault which will be a good starting point for what the problem could be.

Thank you for your quick response.
The mechanic did put a diagnostic tool on the car but found no relevant codes. He cleared all existing codes but that didn't make any difference.
I have a bluetooth OBD11 scanner but don't get anything.

[kamold]

Sounds unusual. I'd still like to see a VW specific tool used to do a scan, generic scan tools can be a bit hit and miss.
But it could be that there is a short somewhere and that is causing the brake to be engaged when it's not. This wouldn't necessarily cause a fault, but could result in the behaviour that you've seen. Finding the short though would require some time and a multimeter, possibly the wiring diagrams. might need to run an overlay harness to bypass the factory wiring to see if that fixes it.

[brad]

There's a brake light switch on the pedal. They are about $10 and are easy to change but there is a technique to it.

There's also a brake light sensor on the master cylinder 8P0 698 459 B these are ~$20 and not hard to change.

I'm not sure why there was "a fair bit of cost".

Suggest you find a mechanic that knows VWs. It will be cheaper in the long run.

edit: also double check that the correct bulbs are installed and all the bulbs are working

[harveyspecter1209]

I have a 2012 Octavia RS. Recently my cruise control stopped working. I then noticed that my brake lights are always on when the car is running. I assume that the two problems are related and cruise control doesn't work because the computer sees the brake as being applied. I had the brake light switch replaced. It is mounted on the master cylinder on my car. After being without the car for 3 days and a fair bit of cost the problem is still there with the new switch. The mechanic had no idea what it might be other than to say it's an issue for an auto electrician. Spoke to an auto sparky who I must say didn't fill me with confidence that he could fix it without a bit of trial and error which would be at my further cost. Has anyone here experienced this issue and have some clues as to what it could be and how to check things and isolate the problem?
ABS or Traction control light on can be more serious. Visit autoguysland website to know how to do when you face this issue.

I think ABS may be have the problem.