BMW 1 Series Coupe Forum / 1 Series Convertible Forum (1M / tii / 135i / 128i / Coupe / Cabrio / Hatchback) (BMW E82 E88 128i 130i 135i)


Post Reply
Thread Tools Search this Thread
      07-10-2016, 11:39 AM   #177
Enlisted Member

Drives: '13 135is + Mini + VW + Ford
Join Date: Jul 2013
Location: DC Metro

iTrader: (1)

Hi All -

I installed a hitch and wiring harness adapter on my 2013 135is yesterday and figured I'd share my experience since I see a lot of the same questions being asked.

I picked up a Curt C111841 (which includes a 1 7/8" euro drawbar) and a Tekonsha Modulite ZCI harness adapter. I picked up the latter since it required no splicing (and should result in no light errors).


Hitch install is just like it says in the directions included with the Curt. Remove the bumper fascia and the plastic undertray thing on the passenger side. The hitch slides right over the bumper bolts with everything else in place.

These are all the tools I used for the install. Well, plus a sharpie and a razor knife.

The exhaust bracket (this is the PE, mind you) was ~1/16" from the hitch bar. This is the view looking up from the ground.

So I marked and cut the bracket.

Cut out the plastic like it says (I had to cut further down in the center section)..

And it fits right in there.



Here's the ZCI harness kit:

It has inductive sensors which snap around the wire.

I started by pulling off the trunk liners, and under the right side carpet is a molded foam support which had an existing electronic module in it, and a slot that perfectly fit the ZCI control module.

I wired everything up using mostly signals from the right side harness, with the exception of the left turn signal. The inductive sensors are slightly bulky, so the challenge was finding locations for them where they wouldn't rub or be crushed in normal use of the car.

Here's the right side...

... and the left side.

Not my cleanest wiring work ever, but it's tested and fully functional.

There's a main chassis ground right near the right tail light, so I used that to ground the ZCI unit, and ran power to the trunk (orange wire in the top right of the following photo). The trailer harness just hangs out in the battery compartment.

And will hang out of the trunk when in use.

I'm not super happy about having it hanging out of the trunk, but I didn't feel like taking the bumper off yesterday. it was ridiculously hot. Maybe that's a project for another time.
Appreciate 0
      08-27-2016, 10:04 AM   #178

Drives: 2012 128CICA SULEV
Join Date: Feb 2015
Location: New Jersey

iTrader: (0)

Originally Posted by Trenchdigger View Post
Update: Yes, it is Curt #11184

I installed it on Sunday. Fits great, no issues on a 2013 128i. I'm using it for a bike rack; plenty of clearance.

Note: I did NOT remove the bumper cover to install. However, it would have been much easier if I had.
Trenchdigger, can you confirm that no trimming was required on your 128i? Did you have any muffler rattling noise after the exhaust gets hot? I am about to start an install on my 2012 128i SULEV 'vert.
Appreciate 0
      01-13-2017, 03:06 PM   #179
Private First Class

Drives: Red on Red 135I
Join Date: Sep 2010
Location: PA

iTrader: (0)

Reviving an old thread. Do you know the wire coloring which connects to what?
Appreciate 0
      02-06-2017, 03:19 PM   #180

Drives: 2012 128i
Join Date: Feb 2017
Location: Riverside, CA

iTrader: (0)

Originally Posted by 1hot135I View Post
Reviving an old thread. Do you know the wire coloring which connects to what?
I just did this whole job on my 2012 128i, installing the trailer hitch and adding the ZCI wiring harness. It was all really easy with the exception of removing the bumper cover. All the obvious and visible bolts aside, the key to getting the bumper cover off is to remember the bolt that is buried beneath the felt near the top of the wheel wells. With the bumper cover off, the hitch took under 5 minutes to put in to place and torque down to spec. I didn't need to lower the exhaust -- maybe that step only applies to the 135i?

For my vehicle the wire colors are as follows (applies to both left and right sides):

Blue/Gray: Turn signal (left side is left turn signal, right is right, of course)
Yellow/Green: Tail light
I seem to have lost my notes about which one corresponds to the brake light, but I think it's yellow/gray.
Appreciate 0
      12-18-2017, 03:52 PM   #181
Brigadier General
JimD's Avatar

Drives: 128i convertible
Join Date: Apr 2009
Location: Lexington, SC

iTrader: (0)

My son and I put the Curtis hitch and a Curtis relay box for the lights on my 128i convertible Saturday. Took us about 5 hours but mostly it was him working and me talking. I used it to tow my utility trailer to the dump Sunday. The European tow bar seems a bit low but everything went well. I used this DIY and it helped. Car barely noticed the trailer. My trailer is a 4x8 from Harbor Freight that is only rated for 1100 lbs. I usually have a lot less on it. I think the bimmer will be fine. We left the plate off that is under the car that you have to cut for the hitch. You can't see the opening unless you go under the car. Wiring is soldered on - that took a little more time but will not turn into an issue later. My wiring comes out the trunk like is illustrated above. I have not done it this way on other cars but if you go under the bumper cover, your wiring mount would be pretty low and a bit of a hassle to use. With the soft weatherstripping on our trunks, having it come out like this is not bad. I decided I need a 5 inch rise for my utility trailer to sit flat. Tallest european mount seems to be just over 3 inches. So I bought a U. S. style bar, Curtis, and ball. Should arrive tomorrow.

Last edited by JimD; 12-19-2017 at 04:07 PM.
Appreciate 0
      02-23-2018, 08:13 AM   #182
Second Lieutenant

Drives: Z3 coupe, 128i
Join Date: Oct 2017
Location: Des Moines

iTrader: (1)

Thanks a lot! Used this to do my install. Much appreciated.
Appreciate 0
Post Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

All times are GMT -5. The time now is 11:39 AM.

Powered by vBulletin® Version 3.7.0
Copyright ©2000 - 2018, Jelsoft Enterprises Ltd.,,,,,,,,, logo and trademark are properties of BIMMERPOST