Troubleshooting Trailer Running Lights Not Working On 2013 Mercedes Sprinter 2500

Published 08/31/2023

Question:

I have a new to me 2013 Mercedes Sprinter 2500 that has an E-Trailer Vehicle Wiring Harness with 4-Pole Flat Trailer Connector unknown model, but similar to Item # 118650. The connector is getting power for the brakes and turn signals, but not the running lights. I have checked the power and ground connections on the black box which are good. I have also confirmed that the connections on the trailer work verified with another vehicle. The drivers side taillight portion of the harness on my harness only has a yellow wires returning to the black box, where Item # 118650 shows yellow and black wires returning to the black box. The passenger side of the harness looks identical to Item # 118650 with red and green wires returning to the black box. Could this be causing the lack of running lights?

asked by: Justin R

Expert Reply:

The fact that your module only has the yellow(left turn), green(right turn) and red(brake) inputs it has no way of getting the function for the running lights off your 2013 Mercedes-Benz Sprinter 2500. Be sure to check and see if the other wire which should go to the running lights were cut. If there is enough of the wire to splice into you will be able to rewire the missing component. Otherwise you will need to replace it with the Tekonsha T-One # 118650 so your trailers running lights will operate.

expert reply by: Bud M