I am having an issue with my 2010 Mercedes C300. In my country, this is a RWD model and it does not have an auxiliary battery, only the main one under the hood.

When I exceed the speed of 23 km/h (approx. 14 mph), several warning lights come on: EBV, ESP, and ABS. Additionally, the power steering becomes extremely heavy, making it difficult to maneuver the car. There is also an error code stating that the tire pressure monitor is inoperative. If I try to use the Cruise Control, another error appears.

This issue first occurred earlier this year; I continued using the car and one day the problem simply vanished. However, a few days ago it returned. I tried the 'lock-to-lock' steering wheel reset (turning it while in reverse), but it didn't work. My first thought was the battery, so I replaced it with a brand new one, but the problem persists.

What caught my attention is the voltage: when I start the car, the battery peaks at a bit over 14V, but then it starts to drop and stabilizes at 12.6V—even with the lights and air conditioning on (this happens with both the old and the new battery).

Could this be a faulty alternator? It is worth noting that when I start the car, no errors appear; the alerts only pop up once I pass the 23 km/h mark.

 

That is about the speed the ABS becomes active. You may have a bad ABS control unit. Other problems could be a bad wheel speed sensor or reluctor ring. All of these systems are related.

A dedicated Mercedes scanner would probably show trouble codes to help pinpoint the failure.

 

If I disconnect the ESP/ABS module in the engine compartment and start the car, will it work?

 

I’m not sure. Disconnecting the module may not cause any more issues than what are already there. But it may be a safety concern and trigger the limp mode where the car can’t be driven more than a few MPH.

 

I thought that disconnecting the ESP/ABS module might prevent the power steering from disengaging when exceeding 23 km/h.

 

I’m not sure, but there are things like complete loss of pressure in the brake system that will put the car in limp mode. If you will only be on low speed local streets near home, try it cautiously.

 

Just to update... the problem has been solved. A scan was run and all errors were cleared, after that no errors returned and everything works fine.