res94025

I installed an OEM hitch on the back of my 2010 GL550 and ran the OEM harness. Everything is connected and the trailer lights don't work. I ran a voltage check at the plug and am getting a constant voltage between 3.5V and 4.0V at each of the pins at all times. No change if a blinker, headlamp or brakes are applied. I know on some of the older models the SAM needs to be reprogrammed but my understanding is that on the 2010 the harness should be plug and play with no re-programming needed. Any ideas? I'd like to avoid the dealer if possible (mostly because it is an hour plus drive to get there).

Thanks in advance for any advice here!

PJsMB

You used the adapter to go from the 7 prong round thing on the MB to the 4 prong on the trailer?

If so, on my 2011, had to get a different adapter (google it) because my trailer had LED lights that didn't pump out enough voltage for my MB to recognize. To the MB, it appeared as if nothing was back there.
2011 MB GL 450 4Matic

kombifan

You'll need to reprogram it and also have the adapter for the 7 way to 4 way to make sure your trailer leds work.