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I'm installing the factory controller and harnesses in a 2015 ML350 (gas engine).
I don't need reverse lights or any of the electric brake controller functions (trailer and motorcycle combined weigh less than 1,000 lbs), just tail lights, turn and brake lights. The usual flat, four-pin plug, stuff.
I bought 246-900-55-01 Tow Control Module, front harness 166-540-44-10 and rear harness 166-440-70-13. I didn't buy a complete hitch kit, so I don't have a wiring diagram or schematic.
The module bolts to two obvious studs under the right rear panel and the rear harness goes out the back to near the hitch receiver, just where you would expect it to. No problem there.
Harness 166-540-44-10 runs from the controller to the fuse block, where it splits. Five of those wires are 16-18awg and have ATO fuse blade terminals, so obviously they terminate in the fuse block. Two additional are a twisted pair ending in a black plug. They are roughly the same length as the wires ending at the fuse block under the rear seat. The second branch contains 5 wires, Four are very long, and run forward to a location under the driver’s side dash where they terminate in the green 4-pin plug (X58/28) that would be used for an electric trailer brake controller. The fifth wire is a single wire terminating in a tiny metal plug that is obviously intended to be inserted into the backside of an existing plug. It is much shorter, and has to terminate somewhere under the rear seat.
I think I have sorted out the landing for all of the wiring except for what I believe are the signal wires, (shown in photos) with the black plug and the single that branches out with the electric brake bundle. These three wires are all very thin wires, on the order of 24awg, data or communications sized, very low electrical capacity, so I think they have to be signal or trigger wires. I am assuming that the single wire that runs with the electric brake bundle is the trigger/signal wire for the brake lights and the twisted pair is L&R turn signals.
Who knows where the twisted pair and the single should terminate?
I have a service appointment at the dealer on Wednesday and I’d like to get these wires terminated so I can get the module enabled then.
Twisted pair, should terminate somewhere in the vicinity of the fuse block under the rear seat
Wow. That is a headscratcher. I am not sure how much help the Dealer will be, I found them to be not that knowledgeable about the trailer couplings, which in their defense, seem to be very poorly documented as add-ons in the factory book.
) transplant of the factory hitch from my 2009 ML350 to my 2011 ML350 with significant wiriing uncertainty, and also having the full factory workshop info with schematics, why don't you PM me and we can exchange some photos and VINs and track that one down like I eventually tracked down my missing (supposed to be missing because no longer prewired, only wired if hitch comes from factory) electric brake controller connector.
05-05-2019, 11:18 PM
