EPC light problem.
 

Good day everyone. I have a serious problem wit my ML 270 CDI. 2004 model. Just for the record, I am not a qualified technician and 61 years old. In all this years I never took any of my vehicles to a garage for a service repairs or overhauls. I did it myself. Just to put things in perspective.

Ok, here is the detail. I bought this vehicle December last year and is still a very proud owner. On my way home, (about 70 km) there was a nice thunderstorm. Next moment the orange EPC light came on and directly after the ABS light. I had to Google to get some answers and yes, the speed control stopped working together with the 4WD. You can't engage or disengage. The mechanic where I bought the car told me they were closing for holiday and I must come back first week in January. The light only went off 3 days later all by itself. Every time I hit a storm same story. They ran a diagnostic and it show the rear left speed sensor did not work. Here is the interesting part. I put a sprayer with water under the car at home and drove forward and backward for about 5 minutes, then hit the road. No lights. A week later very light drizzle and guess what? Lights back on. The problem is not necessarily the sensor. It can be the wiring, the unit, a multi plug or something like that. It is only when it rains The sprayer soaked the car. Any ideas will be appreciated. Maybe if I can find the EPC unit and pull the plug and maybe spray it with electric cleaner?

Sounds like there is a possible short somewhere - are you able to check the fuses to make sure everything is in place?

Thanks for replying. Yip, I pulled all the fuses and made sure they are clean. One thing I forgot to mention is the box under the ABS unit. I pulled the multi plug and cleaned it. You had to remove the headlight to access it. After that was done the light stayed on for only 2 to 3 hours instead of days. It might be just coincidence but the problem does not stay for as long as it did in the beginning but it is there as soon as it rain or when you drive where the road is whet. I did consider a damaged harness maybe?

Hi There to all. Problem solved. This was a rare one but if it can help someone why not? When running a diagnostic test I got a left rear speed sensor alarm. Each and every time. I bought one of those Delphi diagnostic units that you plug into a laptop. Anyway before replacing the sensor I took them off to see if it was possible to swap left with right to see if the problem follow the sensor. You can, though the cable exit the sensor 90 degrees on the left and right hand side of the sensor which mean you had to loop the wire quite tight not to touch the wheel drum. Anyway I noticed a lot off lock-tite and paint on the two torx bolts that lock the sensors. So I cleaned them and put everything back where it came from. Three weeks now and a couple off severe storms, (even today we had heavy rain) and no lights. I did on purpose drove around and through heavy water that was running on the side off the roads and it staid off. The sensor have a brass body that connect via the bolt to the chassis and that is where the bad connection was created. If I took the car to a dealer?....I will rather not speculate. $$$$

Thanks and cheers. :D

Really glad to hear that you were able to address this issue and not have to get the dealer involved. Please let us know if we can assist you with anything in the future!