Laurent1956

ABS, ESP, and (sometimes) BRAKE dashboard codes – These codes popped up on the dash of my newly purchased used 2010 ML550 4matic W164. Before I bought it, the car had recently had its rear brake pads and rotors replaced at a MB, along with a right front axle, by the MB dealership which I purchased the car from. 250 miles from buying this car as-is (internet buy 400 miles from home), the ABS and ESP dash lights fired up and the cruise control stopped functioning. The dash codes came and went, however. The next day, the car went into limp home mode, not allowing the car to shift higher than third gear. After getting the car home, I hooked up my ODB saw that both right wheel speed sensors were reading bad a there was a historical record of diagnostic codes that included electronic overvoltage measured at the ABS, other ESP errors, transmission, etc.. I cleared and tried to test it again. The car popped up the same right and left wheel speed sensor codes, and would apply the brake without me touching the brake pedal. I cleared the codes again, and took the car on a drive while the ODB was running. Within a few miles, both right wheel speed sensors and the brake pad sensor shown bad on the ODB and the dash lights popped up again. However, this condition would come and go and later the BRAKE light came on with the brake pad sensor reading 'on'.
I reported my findings to the MB dealership that sold me the car. They were pretty certain that it was the sensors, and suggested that I replace all four wheel speed sensors. This diagnosis seemed wrong to me, as I considered it extremely unlikely that all 3 sensors would go bad within one instant. I was certain that the fault was the ABS controller, bad cabling, etc. The dealership ended up sending me the sensors (to their credit, and even offered to take the car back if this fix failed), and I had an ABS controller on order just in case. I replaced the right side sensors - and low and behold the car has worked fine since. I’m reserving the sensors the dealership sent for the left side. My guess is that actually not all the right sensors were bad however. Rather, I suspect that the MB ABS electronic front end (circuit that connects to the right side sensors) is not very resilient (e.g., one sensor's (in)operation impacts the readings of other sensors). In my case, only time will tell if I have an electronic condition (e.g., power spike) that will trigger any more events. I would be interested to know if anyone has run onto such a situation.

I'm glad I was asked again (below) as there is a follow-on story to this whole matter that may help others. After I replaced the new sensors, things seems to work well for awhile....but then the system started to unravel once again - intermittent sensor failures with same vehicle behaviors. It was obvious that something else was amiss and I ran out of time and patience. So I tossed in the towel and sent it to my local dealer. The root cause has proven (now that I have tens of thousands of miles behind me) that the rotors were bad - not bad enough to cause notice at the steering wheel, but caused vibrations that apparently messed with the sensors. The brakes were done before I bought the car and through CarFax I was able to see that the service was done at a Sears shop who we could tell used lower grade OEM rotors. After new rotors & sensors, all's been fine since. It was an expensive and at times painful lesson that I'm happy to share.

Cougar6

I know this problem happened 3 years ago, but did it reappear? Did replacing the right front and rear sensors clear the problem. The Exact same problem lights have appeared on my wife's 2010 ML350. I will be working to fix my wife's ML, tomorrow.

Laurent1956

I'm glad you asked as there is a follow-on story to this whole matter that may help you someone else out down the road. After I replaced the new sensors, things seems to work well for awhile....but then the system started to unravel once again - intermittent sensor failures with same vehicle behaviors. It was obvious that something else was amiss and I ran out of time and patience, so tossed in the towel and sent it to my local dealer. The root cause has proven (now that I have tens of thousands of miles behind me) that the rotors were bad - not bad enough to cause notice at the steering wheel, but caused vibrations that apparently messed with the sensors. The brakes were done before I bought the car and through CarFax I was able to see that the service was done at Sears shop who we could tell used lower grade OEM rotors. After new rotors & sensors, all's been fine since. It was an expensive and at times painful lesson that I'm happy to share.