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  1. #1
    Join Date
    Jul 2011
    Location
    Western Pennsylvania
    Posts
    48
    My Cars
    335i 328i, 535xit, ++

    Post E70 trailer hitch wiring issue

    Hello all,

    I have a 2012 E70 and am installing the factory hitch with factory wiring harness 71 60 2 156 525. As farf as I can tell, this is the only harness available for the E70, but it is not the correct harness for N55 E70s that have both PDC and Comfort Access. The problem is with the routing through the body into the car. In early models, the two grommets in the right rear well behind the fuses was were used for 1) Park Distance Control and 2) the Comfort Access antenna. So BMW combined the trailer hitch harness with the comfort access antenna harness so those two items could be routed through the same hole. Starting with the turbo models in 2011, there is an extra element. What looks like a harness or air pressure line for the rear exhaust gate, or perhaps a line for the air suspension, was routed through one of the two grommets and a new combined PDC/Comfort Access harness was routed through the remaining grommet. So now I have 2 harnesses, each with their own grommet, and one hole in the back of the car to fish them through. I looked but can't find a triple combined harness (i.e. hitch, PDC and comfort access), so I'm thinking it does not exist. I suppose I could unwrap both harnesses, combine the hitch wiring into the other harness (discarding the Comfort access wiring in the hitch harness) and re-wrap it all, but that's going to be a major pita. I searched around and saw that others have also encountered this problem, but nobody posted a solution.

    Does anyone have any suggestions?

    Thanks!
    Current BMWs: 14 total. '12 X5, '09 E93 335i, '09 E91 328i, '08 E93 328i, '08 E61 535ix '02 E39 M5, '01 E39 M5, '02 E39 touring, '91 E34 M5, (2)'88 E28 M5s, '75 2002, 74 2002,
    Prior BMWs: Every E-body 5 series including tourings and every E-body 3 series. '74 2002 tii
    First rule of BMW Ownership: Buy a BMW specific scanner!

  2. #2
    Join Date
    Jul 2011
    Location
    Western Pennsylvania
    Posts
    48
    My Cars
    335i 328i, 535xit, ++
    I found a solution to this. The solution is to move the vacuum tube so that it and the existing wiring harness are sharing one of the holes and then use the remaining hole to install the new harness. Leave the PDC and Comfort Access connected to the existing harness and only use the new harness for the hitch. The only wires that need to be connected are the fuses, the ground wire, the hitch controller and the little jumper wire that connects to the tail light harness. There is the hidden hitch documentation that does a MUCH better job of explaining it than the BMW documentation.

    I tried several times to upload the invisihitch installation instructions for the BMW OEM wiring harness but got several different errors. So here is a link to a different thread that includes a link to the file. Hopefully, it will still be there when you need it.

    https://www.bimmerfest.com/forums/sh...d.php?t=719247

    Thanks,

    Scott
    Current BMWs: 14 total. '12 X5, '09 E93 335i, '09 E91 328i, '08 E93 328i, '08 E61 535ix '02 E39 M5, '01 E39 M5, '02 E39 touring, '91 E34 M5, (2)'88 E28 M5s, '75 2002, 74 2002,
    Prior BMWs: Every E-body 5 series including tourings and every E-body 3 series. '74 2002 tii
    First rule of BMW Ownership: Buy a BMW specific scanner!

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