M Klasse Diesel Seat Heater Issue

Seat heaters can be tricky! An error code points to something beyond a blown fuse. When you say it doesn't get warm at all, have you checked the basics like the fuse box? Is it both front seats or just one? If it's just one, it sounds like the heating element itself. Those mats are usually embedded in the seat and can crack or break over time. Replacing them often involves removing the seat cover. Is this something you looked into already?

I checked the fuse. It's fine. Just the driver's side. What's involved in replacing the mat?

Okay, driver's side only and fuse is good. Replacing the mat… first, disconnect the battery. Safety first. You gotta remove the seat from the car, then carefully detach the upholstery. The heating mat is usually glued or somehow attached to the seat foam. It's fiddly work, and you gotta be careful not to damage the seat cover or the foam. Unless you're comfortable with automotive repair and have the right tools, I'd take it to a workshop. A new mat plus labor might run you around 390€. It's not cheap, but having a working seat warmer in winter is priceless!

Thanks for the info. I think I'll let the shop handle it. 390€ sounds about right. I need that seat warmer fixed.