S90 Lighting Fault

That sounds frustrating. I haven't had the exact same issue, but I did have some weird electrical gremlins a while back. Have you tried checking the light switch connections? Sometimes they can get loose or corroded, causing intermittent problems. Also, does it happen more often in wet weather? That might point to moisture getting in.

Thanks for the suggestions! I inspected the light switch connections briefly, but I didn't notice any obvious corrosion or looseness. I haven't specifically noticed if it occurs more often in wet weather, but I will pay closer attention. When you mention 'checking the light switch connections', are you referring to the connection at the switch itself, or elsewhere in the circuit?

I meant checking the connection right at the switch itself, but it might be worth tracing the wires back a bit to see if there are any other connectors or potential problem spots. Given that you're getting a specific error code and the lights are switching on randomly, it does sound like something more than just a loose connection. Probably best to get it checked out by a workshop. These modern cars are quite sensitive.

Thanks for the helpful advice! After considering your input and further research, I took the car to my mechanic. The light switch was indeed faulty. The repair, including parts and labor, came to approximately 95€. Hopefully, this information will be helpful to anyone else experiencing similar issues.