Anthony Porta

After receiving several emails about people who want to retrofit an OEM hitch to their W164 ML's I made a little wiring diagram to help.



You'll need two harness and the correct Rear Sam ( A 164 900 54 01 )

The trailer hitch harness https://www.ecstuning.com/b-genuine-...ss/1644401539/

and the harness that connects the above harness to the rear sam as well as the trailer brake controller harness. https://www.ecstuning.com/b-genuine-...ss/1644402513/

The fuses go into their color matched places in the rear fuse box. Youll also need to add a couple relays to power them so here is a photo of my rear fuse box so you can see what you are missing.



Attached to this post is a pdf with the part number to make a connector for the brake controller so its plug and play with the harness.

Buy your SAM from a reputable dealer (online is ok) and have THEM install it (just the sam have all the other wires run and plug there for them to plug into the sam). because the first dealer I went to shorted out my new SAM and the second dealer was able to replace it and reprogram it because of the parts warranty.

On a side note, I didnt need a new bumper cover either, all I had to do was cut a small portion of mine to fit.

Dinismb

Hey buddy Im doing this right now. I have one question. The multipin white connector, where does it go to? thanks in advance for your help

coyoteinventor

Dinismb, did you ever figure out where the white connector goes? I will be buying both harnesses mentioned by Anthony Porta and I'm double-checking what else I'll need.
I'm getting the hardware from the dealer but they said it does not come with any harnesses. And I'll have to buy the 7-pin socket that goes on the hitch (not mentioned in this thread so looking around for the correct part # in ECS tunning). Is that all I'd need? Hoping to start working on this this coming weekend... :-)

Thanks in advance for your help!

Dinismb

Ok so here is what I did. I took the hitch off of the ML and installed in the GL and I had to do some mods.
First of all, make sure you have a GL hitch if installing it on a GL or ML hitch on ML, as the GL has 2 supporting arms on each end that go as far as the whole trunk space. The ML has only one supporting arm on each side.

As for the white connector its for the brake controller. I left it out as I will never use a brake controller. I took it apart and after realizing I’d have to tear the whole ride side of the car apart I sad funk it. You have to take all the wires apart and follow its wiring through the rear right side panel, and then underneath and all the way to the front of the vehicle underneath the steering wheel. If you remove the underneath panel next to the OBD scanner hookup you will find a blank connector which is for a brake controller.
Then youd have to go to DAS and under the rear sam/ developer mode/ and enable trailer coupling/hitch. Thats it.

The wiring you see above is all you’ll need.

Dinismb

Oh and also, if you look at Anthony’s picture of the fuse box panel, you will need the 2 grey relays on the top right corner on the picture.

wannawagon

with brake controller I haze done it a few times (2 ML and 1 GL) by running three core (normally an offcut of power extension lead as it has tough shething) ,
one feed (taken from bottom right of rear fuse box),
one from brake light (at plug as signal for controller)
and one to the service brake terminal on plug -

run it under vehicle til you get to the plastic under floor pan on right. Run it under these plastic covers, into battery box along inside of centre console and then to drivers area where you want controller . This is just with a normal (Tekonsha etc) type controller.

In Australia we have to run a brake controller "to be operated from drivers position" on any trailer of 750 kg gross weight.