Installing a Universal Trailer Wiring Harness on a 2007 Lexus RX 400h

Published 07/09/2013

Question:

Your instructions, both hard copy and online, are inadequate for this vehicle. Lexus forums report that there may be a prewired connector for this, though I havent found it on mine. Access to the wiring harness is not described at all by your materials, and that seems essential to choose a good mounting point for the circuit and splice points for the wiring. Please provide something that is actually written/photographed for this car and not generic wiring diagrams.

asked by: Thomas M

Helpful Expert Reply:

The Wiring Harness, # C59496, that you purchased is a universal wiring harness that can be installed on many different vehicles. That is why the instructions are generic and not vehicle specific. At this time there are no vehicle specific aftermarket wiring harnesses available for the 2007 Lexus RX 400h.

We have not had the chance to install a trailer wiring harness on a Lexus RX 400h yet so I do not have written material or photos, but I can give you some tips on where to find the tail light circuits to splice into. The easiest place to find the tail light circuits is directly behind the tail light assemblies. You'll want to access the harnesses feeding the taillight assemblies by removing your taillight assemblies, which should be outlined in the owner's manual.

Once you have the tail light assembly out, you will see wires going into the back of the tail light assembly. The wiring kit that you purchased came with a circuit tester. You will want to probe the wires to determine which wire carries which function. Unfortunately my wiring harness manufacturers do not have specific color and function information for your vehicle, so testing the wires will be the best way to ensure you are splicing into the correct wires.

When installing a universal wiring harness, how the wiring harness is installed is at the discretion of the installer. You may find that there is not enough room behind the tail light to mount the converter box, so you may need to look into other mounting options. If there is room under the vehicle, you may be able to mount the converter box somewhere under the vehicle (preferably in a dry location away from dirt, water and other elements) and feed the wires up to the tail light assemblies.

expert reply by: John H