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Discussion Starter · #1 · (Edited)
Posting this in case I need the info in future.
I found very little assistance in executing the project.

Here in Australia, Holden sell the towbar assembly, along with a (expensive) towing wiring harness upgrade that sits within the boot fender.
The cruze wagon has a trailer plug in the passenger rear boot fender for the loom upgrade to plug into.
I am aware that different car models have differing wiring harnesses, so be sure to quote the Vehicle identification number correctly.

I will attach the scanned copied from their online documentation - that came with the kits.
Best ya can do since no hardback service manual.
The pages for the wiring harness were more informative in terms of bumper/panel removal.
The towbar docs were a little lacking in readability I thought.

Note: Below Extracted from website:
Trailer Detection_ This is simply an element of a CAN protocol which is activated usually by the car acknowledging a trailer is connected. This is not done by any mechanical means, but by simply inserting the trailer plug into the towing socket.

The car realises it has a trailer connected and now stimulates certain operating systems to wake up. These systems include:

Trailer Stability Programs_
A change to the parameters of the vehicle’s Electronic Stability System - the car detects the ‘Snaking’ of a Trailer and by activating the ESP sensors in the vehicle, It brings the caravan back under control.
C2 Function_

The C2 function of the trailer is activated, usually by a Double frequency flash rate of the car indicators, should a trailer indicator fault be detected.

Fog lamp cut-off _
The rear fog lamp on the car is switched off when towing if a fog lamp is fitted to the trailer.

PDC Cut-off_ If the vehicle is equipped with parking sensors these will be automatically turned off when a trailer is connected.

The important features of these operations is that they DO NOT function if the car is fitted with by-pass technology used in towing electrics. (eg the curt aftermarkets?)
They will only work when they detect a towing module which is sending and receiving signals through the CAN bus system.

Also, an advisory, it took me by surprise and extra cost.
The towbar & wiring harness do not encompass an electric trailer brake controller.
The wiring harness module is only for communication with the car's computer.
Instead, there was merely a blue wire tail for brake controller connection connection as part of the wiring harness upgrade.
I am not aware of any cruze driver position connection/mounting options for a brake controller.
(I positioned my ebay controller to one side of instrument cluster...)
I ran a fuse wire from the battery(via the firewall wiring loom penetration rubber boot),
and then brought the blue trailer service brake wire from the rear towing module up to the front.
Needed to bring the red brake wire from the rear wiring harness also up to the front. As no up front 4 wire connection for a brake controller like some other vehicles.
As Braking indication must tie off from the added trailer towing module (part of the wiring harness upgrade).
I also brought the two sensor wires indicating a trailer attached up to the front dash as well. Mounted a toggle switch.
Thereby retaining the stability controls and electrical fault detection capability.
I needed to do this since the towing package only came with a FLAT 9 pin socket option. (Not my preference, would have had to use an adapter, and plastic sucks.)
There is a small magnet mounted in the flap of this flat plug that actuates(opens) the embedded socket reed switch when socket flap lifted to attach trailer plug.
The two additional small wires Grey/white) either side of the nine pins are for this sensor connection.
I'm not aware of any small ROUND 9 pin plug that includes a similar magnetic sensor capability.
Tough luck if you have a small round 9 pin trailer, or damage the flat socket flap in any way
(or heaven forbid the magnet falls out).
First you will know is the too fast rapidly blinking indicators as flashing to turn left or right.
The computer has picked up that the right amount of current is not flowing for having a trailer attached.
So outputs the industry standard electrical error signal of increased flash frequency
Our right hand drive vehicles, just run the additional wires within the passenger side interior plastic door sill paneling to get from trunk to front.
Some crazy people have you-tube videos of attaching wire to underside of car - obviously only ever driven on concrete driveways not having wire damaging potential!

I also took the opportunity to run a separately fused cigarette light socket power source to the boot/trunk as well.
Always handy for the kids recharging/mobile fridges.

The cutting of the hole in rear bumper to allow towbar exit was easy, kit includes a bit of rubber moulding to press on its perimeter to make it look good.
And removal of the hatch's interior side paneling and tailgate lip plastic trim wasn't difficult, no special tools. Just be careful when prying things apart.


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