Its not that hard I know, my towbar is a 7 wire unit, the extra's are electric brakes and reversing lights/beeper.
I don't own a test light / multimeter (yet) and I was kind of hoping someone had a wiring diagram so I could be lazy !
From what I have worked out, roughly, the 9 wires I have in the Camry are:
Common - White and Black
Green & Yellow - RH Indicator
Green & Black - LH Indicator ?
Light Green x 2 (Park Lights - one each side?)
Dark Green (Don't know)
Red & Yellow (Don't know)
Green & White x 2 (Brakes - one light each side)
Its the one Dark Green and Red & Yellow I can't suss.
All I have left in the rear is the licence plate lights,
as the reversing lights are on the back of the boot and its
wires run thru the inside of the boot lid.