Mercedes Repair Questions? Ask a Mechanic for Answers ASAP
Hi, what have you checked so far? Have any parts been replaced?
Did you say that the speedometer wasn't working?
Sounds like either a bad ESP module or a bad transmission module. I'd disconnect the transmission module and see if the speedometer works. If it doesn't I'd suspect the ESP module or no power to the module.
It's located in the module box under the hood on the passenger side.
Click on the link below.
It should be right next to the TCM.
The K40 relay in the same box powers the ESP module. You should have 12V on the red/yellow wire at the esp module with the key on.
The red/yellow wire is in the 30 pin connector on the ESP module at position 14.
Can you scan the ESP module for codes?
Since the speedometer is not working I would have to suspect a fault with the ESP module. If the TCM does not receive a speed signal it will go into limp home mode. I'd like to know the codes in the ESP module before I condemn the module. You could swap out the TCM with a good used one as a test. You could do the same with the ESP module. If you disconnect the ESP module can you communicate with the other modules? Is there any sign of transmission fluid in the TCM?
At this point I would either get the codes read with a Mercedes tester that can read all of the modules or I would try a used ESP module. If you have no success I would try a used TCM but the fact that the speedometer is not working leads me to think that the ESP module is faulty or there is a wheel speed sensor failure.
Not sure if I trust your scan tool. Ideally I'd like to see the car connected to the Mercedes Star Diagnosis tester. Since you have no speedometer I'd try a used ESP module.
Electronic Stability Program. It's the same as the ABS module.