2011 LX570 / LC200 Trailer Harness - No tail lights on trailer and loom questions

[LXS]

Hi have an Australian delivered LX570 with a 12 pin trailer plug installed. I am having trouble with the trailier taillight / marker lights (pin 7). While all other pins work (so far as I can tell) this one is not working. The lights on the trailer definitely work as a I have checked by applying 12v to the pin on the trailer-side plug.

Things I have checked:
- all fuses; and
- have dismattled the 12 pin socket and checked pin 7 for power (nothing).

I am now trying to work my way back up the harness but cannot for the life of me work out how its all plugged in. The harness loom seems to go up to the taillight of the car (where the jack is stored) but then appears to go under the rear floor area again. I'm hoping someone here might be able to tell me where the next point to check with my multimeter might be before I fully pull apart the whole rear section of the car! Pictures would be appreciated!

Note: I had thought it was just a simple plug and play loom under the rear of the car, but it seems to be a little more complex than that so far.

 

[Sandroad]

I’m ignorant about the12 pin connector but be sure you have checked ALL the fuses marked for towing with your multimeter since even bad fuses can look ok. Also, is there any chance a relay is involved in circuits to the 12 pin connector? And also, is there any chance the taillights have a separate ground associated with the 12 pin connector? In my experience trailer light problems of all sorts, including those originating in the tow vehicle, are often caused by bad grounds.