Car ran fine Monday November 30th, 2020. Car then sat for two days. After starting the vehicle after the two days, I got error messages stating my distronic plus, pre-safe braking, and blind spot assist systems were disabled. When I put it in drive, there was a very harsh engagement. I didn't realize the car was stuck in limp home mode until I turned out onto a busy 45mph road from my neighborhood and the car would not shift at all; there was no message notifying me that the vehicle is now in limp mode. After reading codes and verifying power to fuse 33 (the TCM fuse), I realized there was no signal from the module; it was not operating at all.
I ended up limping the car 25 miles to my trusted independent mechanic, who was a Mercedes-Benz technician for 15 years, and he diagnosed a bad TCM (which is what I suspected). He has repaired multiple 7G-Tronic transmission failures due to a bad conductor plate, and the TCM is integrated into this conductor plate. This unit requires SCN coding, and it wasn't only until recently that Mercedes-Benz started to allow independent mechanics to obtain the part.
I understand it is a complicated vehicle built to a precise standard, but for a transmission that has been in production since 2003, I would have hoped Mercedes-Benz would have made the transmission less failure-prone for my 2010 model year vehicle.
Car ran fine Monday November 30th, 2020. Car then sat for two days. After starting the vehicle after the two days, I got error messages stating my distronic plus, pre-safe braking, and blind spot assist systems were disabled. When I put it in drive, there was a very harsh engagement. I didn't realize the car was stuck in limp home mode until I turned out onto a busy 45mph road from my neighborhood and the car would not shift at all; there was no message notifying me that the vehicle is now in limp mode. After reading codes and verifying power to fuse 33 (the TCM fuse), I realized there was no signal from the module; it was not operating at all.
I ended up limping the car 25 miles to my trusted independent mechanic, who was a Mercedes-Benz technician for 15 years, and he diagnosed a bad TCM (which is what I suspected). He has repaired multiple 7G-Tronic transmission failures due to a bad conductor plate, and the TCM is integrated into this conductor plate. This unit requires SCN coding, and it wasn't only until recently that Mercedes-Benz started to allow independent mechanics to obtain the part.
I understand it is a complicated vehicle built to a precise standard, but for a transmission that has been in production since 2003, I would have hoped Mercedes-Benz would have made the transmission less failure-prone for my 2010 model year vehicle.
- Calvin O., Commerce City, CO, US