RH Rear tail light failure

[CraigE]

Ok a bit of an odd one. Last night while travelling home we lost tail lights on the car and van. Was a bit strange, they were working when I indicated to turn into Kumarina Roadhouse, but when I pulled up nothing. Left hand side still working.
Doing some fault finding today I still have power to the green plug CO537-2 but none at the rear CO125-3. Is it likely that there is a splice for the trailer wiring somewhere and this has come adrift or could the side fuel tank that I have fitted about 6 weeks ago could have crushed some wiring?
Was working fine up until now.
I am a at a bit of a loss as I can see the only real solution is having to re run wiring back to front.
Brake lights, indicators all still work fine.
It is fed off of fuse 12 and that has not blown which sort of indicates it may not be a short.
As a temporary measure I have run a wire from the LH side to run the tail lights, but trailer lights still do not work.
Looks like a nightmare to try and pull the harness.
Any ideas?

[dmdigital]

The trailer wires should be spliced in on the RHS. There's actually a plug there for them. Should all be in parallel so if trailer light is out shouldn't effect tail light and vis-a-vie.

See if you can locate the wire at the front (fuse) end and test it there. From memory they all run inside the chassis rail to the rear.

[CraigE]

The trailer wires should be spliced in on the RHS. There's actually a plug there for them. Should all be in parallel so if trailer light is out shouldn't effect tail light and vis-a-vie.

See if you can locate the wire at the front (fuse) end and test it there. From memory they all run inside the chassis rail to the rear.

Thanks,
Have determined there is power from the fuse out to the plug in the engine bay under coolant resevoir, from there it goes to the chassis rail and back. Trying to work out where it fails is going to be the difficult part. The really crappy thing is I have to pull out the aux fuel tank to access the back panel in the wheel arch where the wiring feeds up.