Wierd cutting out problem with w204 c220

[Zu11y]

Hi guys
I have a 2013 w204 c220cdi and it cuts out when you either switch the headlights or sidelights on. If they are off the car will run spot on all day.

This is a wierd fault. Our snap on machine says that their is as implausible signal on circuit 15 and also giving a voltage error with the aux battery.

Any idea on this one guys?

 

[Ted]

Circuit 15 is ignition.
My guess would be a faulty common earth between an engine component/cpu and the lights.
I would check for an earth stud with a lot of brown wires on the inner wing near the headlights. Check and clean on both nearside and offside.

 

[Zu11y]

Thank you for your reply, that is the first thing i have checked and all the visible grounds check out fine i will double check tomorrow