Mercedes CLS 2018 window not working

Page may contain affiliate links. Please see terms for details.


New Member
Jan 11, 2023
Mercedes CLS Prem+ (C257)
Hi All, I have a 2018 Mercedes CLS (C257) and my rear passenger window on the drivers side does not open or close. The weird thing is that the soft close when opening and closing the door works. When you open the door, the window goes up a bit and down when closing the door.

Took it to an independent garage and they couldn't find anything wrong with any of the parts so they are assuming it's a software issue. I also unplugged the battery of the car for about 15 minutes and also changed the fuses for the door control module. And still no luck.

Trying to get any information from anyone who knows what the issue could be before I cough up £204 at Mercedes Benz for an inspection.

- Passenger rear window does not open or close (even tried using the key to open the windows from outside, all other windows open apart from that window)
- Disconnected the battery for a while
- Checked fuses
- Tried some window reset stuff such as holding each window button down for 10 seconds and up for 10 seconds
- Took it to an independent garage (luckily they did not charge)
- Soft open and close works when opening/closing door
- Window still not working

If the window goes up and down a bit when closing the door, could it not be a sort of break in the cabling
The SAM unit may have failed/be on its way out.

A diagnostic machine scan should confirmed this.
Last edited:
Thanks for the replies. I took the car to another independent garage and they had better luck than the first, not sure what the first set of "mechanics" were doing. They plugged it in to Xentry and only 1 fault code appeared:

B18B82A - Switch "Right rear power window" has a malfunction. There is no signal change.

The guy used Xentry to operate the window and boom, window moved up and down without any issues, he then cleared the fault code and now the window operates as normal. He did say that if the issue persists then its probably the control module that will need replacing. He did say while it was plugged into Xentry, he could see the signal going up from the drivers door but not down, and down on the actual door but not up. However, none of the switches worked in the first place. Couldn't figure out what caused the issue. This whole process didn't take long and nothing was done to the car so I didn't pay much to get it "fixed"

A bit of a strange one but hey, we move on.

Users who are viewing this thread

Top Bottom