Sorry if this has been covered before but my search skills are blah... anyways long story short after hooking up my trailer to the lx470 I had some odd electrical issues. I didn't make the connection at the time but basically while testing the lights only the right turn signal would work properly. The left turn signal would flash once, and the brake lights just did not work at all. Hazards also only flashed once.
Car was working great before, no flaws or problems at all, so I knew it was the trailer or the electrical harness on the trailer (I've towed other trailers before and they've worked fine with the lexus as well). I'm pretty sure this has to do with the fact that someone sideswiped the rear left brake light assembly probably causing a short with the left signal/left brake light.

Oddly enough this somehow killed the brake light switch as I no longer have any brake lights and can't shift out of park. Easy fix (I hope it's just the brake switch, the fuse next to the drivers kickpanel for the brake lights seem fine, didn't see any smoke either), but that made me wonder, are the tow package electrics just straight hooked up to the brake & signal lights? I thought these systems are usually isolated in some way.

The brakes and lights are connected to the 7 pin socket (T12) through several relays (towing converter relay T15, towing hitch relay T23) and the towing brake controller T18. I don't know how to add an image of the actual schematic. These numbers are from a 2004 Land Cruiser Electrical Wiring Diagram, but match my 2002 LX470.