Bought my 2003 GX last year. The car was not prep for towing. Installed a factory hitch, towing wiring harness that plugged into pre-existing connectors near the spare tire, and the towing tail relay. After all this, I can't still get my boat trailers' brake and turn signal lights to work. Had my trailers' lights checked and everything checked fine. The dealers in California are useless. They can't figure out the problem unless I'm willing to commit $600, which I don't want to. Anybody know what I need to do? Am I missing more relays? Please HELP.

Under the left end of the dash is a connector for a brake controller (wrapped in foam with a rubber band). I suspect that you need to jumper this connector to send power to the hitch wiring at the receiver location.

Hope this helps.

Bruce

Since the vehicle didn't come with the tow prep, he's actually missing the relays. Two relays are needed for the underhood fuse box and one for the tow converter box which I believe is in the rear under the tail lamp .

When I did mine (same circumstances), I had to pop one relay in the from box and one behind the tail light (see the photo, the relay is the green box).

A lot of people will tell you that all you need is the relay under the hood, but they rear relay is key. Why? because if you plugged the wiring harness in under the truck, by the spare tire and the relay under the hood, but not the green relay, a volt meter will show weak current when you check continuity at the harness. The green relay is available via mail order at Sewell Lexus.

Photo Attached.

Good luck!

Joe

Hello,
Does anyone have the part number for these relays? The two relays that are needed, one for the underhood fuse box and other for the tow converter box? and where does the fuse box relay go?
I have a 04 GX 470 that was not preped. I got the hitch and harness, but aside from the ground wire, none of the other lines are hot. I only get .01 volts on the aux line. All other are dead, no signals or brakes.


Thanks.

I found the part numbers for one of the relays(had to sub to TIS) and the tow brake controller. I don't know what that looks like, but based on the location on the diagram I have, I think that is there:

T13 Towing Converter Relay 90980–11535

T 8 Towing Brake Controller 90980–11603

I'll post the part number for the other Tow Tail Lamp relay(the one under the hood) when I find it. If anyone else has that, please post it.

Thanks.

I have a 2004 GX and it has the bumper (tow) cover on the back (sorry if I am not calling it by the correct name), how can I tell if it has been 'tow preped'?

Do I just pull on that cover with my hands to remove it? Sorry if that is a silly question, I have never messed with towing stuff.