Problem installing OEM hitch and harness
 

Hi All:

I got the following OEM part numbers for my E70 vin 0E08575:

71-60-2-156-525 trailer hitch kit
71-60-2-185-557 trim piece kit
71-60-0-413-358 ball mount kit

All was going well with the install till I got to the wiring.

1. Both of my wheel well passthroughs are taken, as shown in attachment 1.
2. The convenience antenna two wire connector and the six-pin PDC connector that goes to the sensors on the bumper fascia go through the pass through on the right (see attachments 2,3 of the connectors on the harness and the connector on the fascia.)
3. I feed the PDC/comfort harness through he passthrough into the wheel well as indicated in the instructions.
4. I feed the harness from the trailer hitch kit through the pass through.
5. I hook the old comfort antenna two-wire connector to the trailer harness in the wheel well, and hook the other end of the passthrough on the trailer harness (near the hitch) to the antenna; and, I hook the three pin BUS connector on the trailer harness to the car harness in the wheel well.
6. The problem I have is, there is no provision on the trailer harness to pass through the wiring for the PDC sensors on the bumper fascia (the six pin connector)! The instructions make it sound like it should be obvious/simple, but I don't see any way to make this work. Even if there was some way to pass the wire back through the wheel well, the PDC/comfort harness (now hooked to the pass through on the trailer harness) is not long enough to reach the fascia connector.

I'm obviously missing something, it appears I have all the right parts. How do I get the PDC sensors connected? If I can't figure it out, I'm going to have to take the whole mess to the dealer (who will surely charge the "you tried it first" premium...).

Any help appreciated!

I dont know for sure, but I think you remove the existing comfort access wire, install the trailer harness- there are conductors in the new trailer harness that replace the CA piece that comes out of one passthrough- I think.

Here: Sounds like you pull back the CA (comfort access) wire, into the fuse panel area, with the grommet attached- bundle it up nice and neat, then plug the connector that USED to be at the bumper into the connector that is now on the new harness (which goes through the passthrough vacated by pulling the old wire back.) There is now a new CA connector out at the bumper to connect to where the old wire connected.

Id need to print out the instructions AND have the parts in front of me to determine.

Yes that's correct, there is a pass through on the new harness for the comfort antenna, it's a two-wire connector. The problem I'm having is there is no corresponding passthrough for the six-wire PDC sensor connector (the proximity detect sensors on the bumper). The grommet I have to take out has both the PDC and the comfort connectors on it, but the trailer harness grommet I replace it with only has a retrofit pass through for the comfort antenna connector. So, I can't reconnect the PDC sensors. I have to assume there is some kind of provision for this and I'm missing something, because the dealer would have to patch this in. Unless there is another harness part number that has a passthrough for both PDC and comfort antenna connectors on it...?

Why didn't the PDC remain on one of the passthroughs? The one for comfort access has to be removed, and the pass through used for the trailer harness. The trailer harness has both an inner and outer connector for the comfort access antenna and its harness no?

I'm trying to recall from when I did the install over 5 years ago, but that is how I remember it

The problem is, there are TWO circuits on the one grommet that I have to take out and replace with the trailer harness. The two circuits are the comfort access antenna (two wires, one connector) and the PDC harness (six wires, one connector). When you pull that two-circuit harness into the wheel well and replace it with the trailer harness, the trailer harness has a retrofit connector only for the comfort antenna (two wires), not for the PDC (six wires). I suppose I could drill a third hole in the wheel well so I have a dedicated grommet hole for the hitch, but that seems really lame and un-necessary.

Can you fish the PDC wires through one of the grommets of the pass throughs?

I did this 4 years ago ...

May be these 3 pictures will help:

I was looking back there today and noticed a grommet with blue wires laying in the rear wheel well. I can only assume it was removed and replaced with the trailer hitch wiring grommet when the dealer did it back in 2009. I have PDC and CA.

You wonder if this helped the OP....:cool:

Someone should bookmark this one for "Im doing my hitch wiring questions"!!

Excellent photos! Did you do the install? Was the left grommet slot blank before the install?

Talk about meticulous if you have these photos from four years ago. This is great info, what this shows me is that your trailer harness goes through the left grommet hole, not the right one (where the PDC/CA harness goes through.) My problem is the left hole is already occupied with a pretty sizable harness that feeds through and then makes an immediate turn behind the heat shielding, never to be seen again. No clue what it is for. So you're kinda confirming that if you have PDC you can't use the right grommet hole unless you figure out some way to feed a PDC harness through the trailer grommet. That's getting into some surgery I'd like to avoid. I also thought of just drilling another grommet hole, but the space in that area is pretty restricted, it would be pretty kludgey.