S660 Electronic Parking Brake Failure

That sounds like a pain. I haven't had the exact same issue on my S660, but I've seen similar problems discussed online. When you say it doesn't engage or disengage, does it make any noise at all, like a motor trying to work? Is the warning light constant, or does it flash? Did you check the brake switch?

Good questions! No, there's absolutely no noise when I try to use the parking brake. The warning light is constant. I haven't checked the brake switch yet - I wasn't sure where to find it. Is it easy to access?

Okay, no noise and a constant light does point to a motor issue, or possibly a deeper electrical fault. The switch is usually near the handbrake lever itself. Since you're not hearing anything, and you've got an error code stored, it does sound like the electric motor in the brake caliper could be the culprit, like a defective part. Honestly, with modern electronic parking brakes, you're better off taking it to a workshop that can properly diagnose it. They'll have the right tools and experience. The repair cost for replacing that motor is probably around 505€, but it depends on the workshop.

Thanks for the advice! I took it to a workshop and you were spot on. It was indeed the electric motor in the brake caliper that was defective. They replaced it, and the parking brake is working perfectly again. The final cost was around 500€. Thanks for pointing me in the right direction!