Help needed, pictures of AHM hitch harness connections.

[TriX5]

Fellow E70 owners!

Please, anyone who installed the OEM hitch harness and AHM module, I am trying to understand how the AHM and the hitch harness connects to the E70. I recently bought a used OEM hitch and AHM module for the X5, but the harness connector to the AHM had been cut off. Since there is only one port on the AHM I take it that the harness has more than one connector, the one to the module and another to the vehicle, presumably the CAN bus. The harness did come with one small connector that look like it connects to the PDC sensor but I don't understand why that would be the case. Soon I should get delivery of a plug connecting to the AHM, I bought a used pigtail but I realized that I am possibly still missing a plug to connect to the bus. Anyone who installed the OEM kit, it would be really helpful if you could post or PM me some pictures of the various items the harness connects to.

[andrewwynn]

Attaching to the pdc system prob to communicate to the car to not beep the PDC when trailer attached.

[TriX5]

The instructions in Ista are very limited. I was hoping to find the complete retrofit guide but apparently no such thing. Found the wiring assignments in Ista, going try make some sense of it today.

Intercepting the reverse signal at the hitch socket is counter-intuitive as the trailer module and the PDC module neighbor each other in the trunk I think. If the sensor wire connected to this plug, there would be no connection to the actual sensor in the bumper. Could be for the auto hitch but that is not shown in the wiring diagram. EDIT: Mystery plug is for CAS antenna module.


EDIT: Found the below with a google search, Xoutpost contains so much excellent infomation :-) This is perfect, when my pigtail shows up I will disassemble the harness and discard what I don't need. The solder in the pigtail and it should be ready to code.

[TriX5]

Only thing left that I don't yet know is where the single wire connect (Blue/Brown lighting signal). Anyone?

[Zulu95]

From the complete install instruction I received with my hitch:

14. Carefully route single blue/brown wire from
trailer wiring harness along existing
harnesses to area behind right tail light
assembly. Secure all harnesses with wire-ties
(3) & (4) from installation kit.
15. Locate and remove Connector X318 (1) from
Tail Light Assembly.
16. With connector X318 (1) removed from tail
light assembly, use BMW approved tap
connector (3) p/n 61 13 8 364 566 [included
in kit] to connect blue/brown wire from trailer
wiring harness (4) to the blue/brown wire (pin
3) in the connector. Make certain single wire
from trailer wiring harness does not protrude
from tap connector.
17. Reconnect connector X318 to tail light
assembly.

[TriX5]

Thanks Zulu95. At least I have a starting point, it's an input to the AHM, not an output. I'll run down what that connection is for, I don't like splicing stuff without knowing its purpose......

Last year I installed a European after market trailer module and piggy-backed some spade connectors into the taillight plugs (to avoid the destructive tapping method) It worked fine but the PDC screaching each time I backed up with the bike rack attached was getting on my nerves. (For some odd reason I did not find any OEM AHM's on offer in Europe, neither new nor used.)

The harness that came with my US hitch has some duct tape wrapped around it near the socket, somebody already been messing with that, clearly this is going to be fun..... :-)

[TriX5]

Located the male three pin connector for the CanBus/FRM connection in the back of the car, it is directly underneath the RH outer tail light, now need to find a three pin connector to match. (Worst case I can just use three male MQS pins and wrap them with electrical tape.

Took the duct tape off the harness and no damage underneath it and so at least no funky fixes to deal with. The single Blue/Brown wire connects to the wire for the RH indicator light. No clue why the AHM would need that as an input? I thought any input for the AHM would come via the FRM wire or the CanBus?

So, I have the connections pretty much figured out (apart from the wires that need to connect in the fuse box) and now just waiting to receive the pigtail for the AHM.

Thanks for the help so far, I am sure coding will be interesting as it involves adding to the FA..... :-)



AAAAA

[TriX5]

Spent quite a bit of time researching the wiring for the AHM and discovered that in essence there are two main variants; the AHM3+ and the AHM4R. (There are earlier versions but they don't seem to play a role for newer cars.) The 3+ seems to have been phased out late 2007 which makes me wonder if that was a model intended only for the e53?

Between the 3+ and the 4R unfortunately the plug on the harness changed from 16 to 20 pins. Pin and wire sizes were changed as well. There is an instruction bulletin from BMW how to change the pin assignments when changing from the 3+ to the 4R. I deduced what the pinouts are for both but unsure where to go from here. I am now faced with having a 3+ module and a 4R plug. I can work around that but wondering if the 3+ even works in the E70. Anyone on here know which module they are running?

[Zulu95]

https://www.turnermotorsport.com/p-1...uine-bmw-part/

[TriX5]

Got a pigtail-plug for the 3+ and a used AHM4R for a couple of Jacksons. So, I have two shots at this. From the descriptions and discussions on the german sites the biggest change in the AHM4R is the larger current capacity for the lighting circuits and the inclusion of the automatic (retractable) ball hitch.

Just as an aside, for the retractable hitch there is a secondary module to be installed. A third module is for the trailer brake control. I spent the better part of an afternoon searching for information as it is rather dispersed. My ISTA version only has very limited info.