Focus mk3 2015 right breaklight lit

[mmt75]

Hi,

Focus mk3 2015 1.0 ecoboost estate, right breaklight is lit all the time. I've swapped the P21/5w bulb, which did not help. Any advice on the rear light cable connector pinout, to validate if the voltage is high for incoming signal or the light structure has problems.

[unofix]

Hello Miika from Nottinghamshire 😀

You have a faulty earth on the rear light cluster. It is either missing or is corroded and has a high resistance. Check the light cluster on the other side to the one with the light on for a poor earth.