Problem installing OEM hitch and harness

[dglcinc]

Originally Posted by smassey321

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.

Thanks good photo! Yes, that's the way the install is supposed to work, you pull the old grommet through and put the trailer one in. Interesting, in your picture I can't see any wires coming out of the wide end of the grommet. Perhaps the dealer modified the harness? It would be interesting to know which of the two holes your trailer hitch harness passes through.

[PAX5]

Originally Posted by dglcinc

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.

Yes, I did the install. Took me a day-and-a-half to sort out and decide which way the wiring should go. I just sat on the ground, staring at the wires (having a beer or two) and rationalizing which way things should be connected, all the while reminding myself that BMW would not design something like this if it required cutting and splicing ... so:

Trailer harness goes through the left hole. Whatever is there now, should be traced, disconnected and pulled inside the wheel well. I believe that one side had CA and one side had PDC. I combined the two to come out of the right hole.

The new trailer harness with blue/black connector needs to be taken apart so that it will fit through the left hole going into the wheel well where it needs to connect to the AHM module.

Cap and tie the CA connector that is part of the trailer harness. You won't be using it.

You will use the CA and the PDC coming out of the right hole that was originally already connected to your car.

Follow the instructions as per attached PDF.

I discussed this with Daryl from Invishitch. He wrote the installation PDF.

[dglcinc]

Originally Posted by PAX5

Yes, I did the install. Took me a day-and-a-half to sort out and decide which way the wiring should go. I just sat on the ground, staring at the wires (having a beer or two) and rationalizing which way things should be connected, all the while reminding myself that BMW would not design something like this if it required cutting and splicing ... so:

Trailer harness goes through the left hole. Whatever is there now, should be traced, disconnected and pulled inside the wheel well. I believe that one side had CA and one side had PDC. I combined the two to come out of the right hole.

The new trailer harness with blue/black connector needs to be taken apart so that it will fit through the left hole going into the wheel well where it needs to connect to the AHM module.

Cap and tie the CA connector that is part of the trailer harness. You won't be using it.

You will use the CA and the PDC coming out of the right hole that was originally already connected to your car.

Follow the instructions as per attached PDF.

I discussed this with Daryl from Invishitch. He wrote the installation PDF.

Brilliant! That was the missing piece. I think because the BMW manual was written in 2008, that was before the turbo (?), so it does not have the detail about the inner port having a vacuum hose in it. I have the turbo model, which has a vacuum controller to control the exhaust port. THAT is what is going through the inner port on mine (as described in the manual you attached, which is more up to date.) That tells me what that thing is on the inner pass through, it's a vacuum hose. So, now I know that I need to reroute that though the outer grommet using a fish wire, and VOILA! All is as it should be, and I have the inner port available to install the hitch harness. Bless you. If you come within pouring distance I owe you a beer.

So did you get the retrofit coding for the hitch and if so who did it and how much?

[PAX5]

Originally Posted by dglcinc

Brilliant! That was the missing piece. I think because the BMW manual was written in 2008, that was before the turbo (?), so it does not have the detail about the inner port having a vacuum hose in it. I have the turbo model, which has a vacuum controller to control the exhaust port. THAT is what is going through the inner port on mine (as described in the manual you attached, which is more up to date.) That tells me what that thing is on the inner pass through, it's a vacuum hose. So, now I know that I need to reroute that though the outer grommet using a fish wire, and VOILA! All is as it should be, and I have the inner port available to install the hitch harness. Bless you. If you come within pouring distance I owe you a beer.

So did you get the retrofit coding for the hitch and if so who did it and how much?

Ah, you are in NJ. You are in luck ...

Contact Okee at 585.496.464. Tell him Gerry from Allentown send you - CodeMyCar – Specializing in BMW & Mini Cooper Coding & Programming and pay to have it done, or DIY with BMW Rheingold (do a Google search. CAUTION: not for the faint of heart!).