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.