The harness is 31664746. It’s the US market version (4 and 7 pole connectors). It’s the same for both the OEM foldable hook as well as a non foldable one. So in my case, the red connector is not used (button for foldable hook in luggage department), the blue (electric connector to the foldable hook, and the orange (not sure – supposed to be connected to some versions of the TRM module).
The TRM is (for non foldable hitch) 31454602, note that the actual module inside says 31454600 (?). I was under impression the 02 was a successor to the 00 but it maybe it’s software change only?
The two wires form the car that plugs into he TRM are circled in yellow – they are tucked in there, and you can recycle the foam for the extra connectors we have in the harness.
Once all is installed, I tried the trailer lights and no action. Software for the car is required. The instructions call for 31435640, but we actually want to download 31435638 that is for non-foldable trailer hook. 13 pol version is for EU trailer hitches – different connector.
Note that the software will not show up if you scroll for it, since it was not offered for US V90s. But if you do a “Manual Order” – you can find it and it downloads OK since the VIN check is OK (the car can do it). If you have never bought software through VIDA before – it’s not super easy, but the instructions on the Volvo website are quite good. You need to pay the 3 day VIDA license at the highest tier in order to get sfoftware access. And then pay $50 for the software.
After a few movements and progress bars you see this: success!
Plugging in a tester – it’s working! Oh yes, you need to buy an Amazon tester or have a trailer avail. TRM does nothing until it sees a trailer.
The car now sees the trailer, asks for you to do a light check and also disables cross CTA and parking aid in the rear etc. Pretty darn sweet!
So – in summary – at least up to 2019 – I bet ALL V90s can have the trailer functionality enabled, and you can use the Curt receiver on an R-Design.