KristanToronto

I have a 2015 GL450 and we tow a travel trailer. We currently use a Tekonsha Pridigy RF to tow with as it is wireless.
I would prefer to have a wired brake controller but I can't figure out where to hook one up. I've spoken to numerous dealers and no one seems to have any information when it comes to brake controllers. No one can find a wiring harness for it.

Any help would be appreciated.

fabbrisd1

If you have factory installed hitch - then you will find the connector in one of two areas - cabin inside firewall - zip tied up near brake harness - or "sometimes" under driver's footwell carpet. Use a strong flashlight for the search - can be a little contortionist to find..

andedave

Did you find the harness and install a controller? Any advice or issues that you can share. I'll be purchasing a boat soon to tow - I understand that MB and other EU vehicles have had issues with trailers with LED lights and wondering if that's still true with the 2015. Hope it worked out for you.

fabbrisd1

I have found 2015 GL's with factory installed trailer hitch to be more "tolerant" on LED trailer lights - however if on hookup you have a issue - then Towready makes a adapter with built-in resistor that many of my customers have used with no problem

Wilde

Reviving this thread to see if anyone can help me find the wiring harness for the brake controller. We have the tow package on our model. I just looked under the driver's side dash and can't even see where I'd need to start in order to get to the wires behind the plastic. Anyone able to help?

fabbrisd1

You will need strong flashlight + and be limber on-your-back contortionist

You are looking for a green-plug/socket - which will be attached to about a 10"-12" wire lead - and that lead/plug will be zip-tied or wrapped to other harness wiring.

Easiest to try to spot the green-plug - cut adjacent zip ties or wire wrap tape with a diagonal clipper - frees up the 10"-12" wrapped up lead.

1) Can be up/under driver's side dash in same wiring area as the hood-release/OBD port

2) Can be up/under dash - on the cabin firewall - in the upper area behind the upper brake pedal mechanism

Good luck !

skw

Just to tag on here as I installed a Tekonsha P3 last summer to tow a travel trailer. Remover the lower dash cover just under the steering wheel. Check to see if it is zip tied to any of the wiring behind the OBD port or in that area. Mine wasn't. Next, pull the carpet in the driver's footwell area. I spent 2 days looking and finally gave up. Went to the dealer and they ended up finding it under the carpet near the base of the gas pedal. Guess I did n't pull the carpet back far enough.

fabbrisd1

Yes - starting very-late-14's/15's + - yes it now can be under the carpet by gas pedal.

Remember - this controller plug is with factory installed hitch ONLY - no-hitch/aftermarket-hitch - no Green Socket

Ericlojo

Sorry to hijack this, but it is related. According to the user manual a 2014 GL with 360 Camera and a trailer hitch should have a view splitscreen option when shifted into reverse called "Top View and Trailer View" which shows a trailer coupling view. Can anyone confirm this? Pictures?

ML_Lover

I can verify this, it has many camera angles including the overview of the hitch area with a line to follow.

Also, it you have the factory installed hitch, you will have the brake controller connection behind the carpet under the driver's side firewall at the bottom, its really down behind the brake pedal. As stated in an earlier post, you must remove the shield from below the drivers dash, pull the carpet back and then you can access. Its normally zip tied to a loop so it may be low but if you have the factory hitch, you have the connector. 4 wires, splice them into the pigtail and you're ready to go. I have done this myself on both ML's and GL's. Takes about 30 minutes if you know what you're doing.

thegorilla

Thank you! I had a hell of a time finding the wire as I could see what looked like it at the top of the carpet but there was no way to pull the carpet back because it was far too stiff. I had to remove the kick pamel on the side. The way to remove it was to pull it straight towards the rear of the car at the top and then straight up at the door sill area and then pull the entire assembly towards the rear. The pigtail did not budge 1 cm until I removed the kick panel trim and then pulled the carpet back even more. After that it was cake.