2000 Mercedes Benz C230 4 cyl Two Wheel Drive Automatic
The vehicle is in limp mode, esp bas and hand brake lights are on in dash, the speedometer does not work.I have verified the codes and they are Po720, speed sensor malfunction, also P0500, speed sensor related. This all occured after I changed the spark plugs, but I have been told that this is just co-incidence by mechanics. I was told by Mercedes that it could possibly be the esp unit, but that they would have to change this part first before they could go on with the testing, because they were getting a comunication error from this unit. In the meantme they did not find the problem and still charged me 3 hours labour. Has anyone had a similar problem. Thanking you in advance.
As the mechanics told you I would be very surprised if your changing the spark plugs had anything to do with this. It is more than likely just coincidence. But what they are telling you is true in regaurds to the ESP Control Unit and having a comm error with the unit. Basically the control unit has stopped communicating with the rest of the vehicle and in order to diagnose further they are going to need to have a control unit that will talk to them. Once the failed control unit is replaced it will be able to tell them if there are any other faults in the operating components of the ESP system. However knowing this system these speed sensor faults are probably related to the control unit itself. Therefore by replacing the unit you may fix the rest of the codes. As for the 3 hours labor for telling you that they have a comm error with the ESP unit, this is excessive in my opinion. Most techs would be able to tell you this info within a much shorter period of time. When they run their first diagnostic test they will be notified of this comm error.