Installing Wiring Harness on 2009 Lexus RX350 with Factory Tow Package

Question:

Original car window sticker says: Towing Prep Package includes: Transmission cooler, heavy Duty Alternator and Radiator does not include ball mount It says nothing about wiring. In the tow bar and wiring package I bought from etrailer, it looks like I have to run power from the battery and then use a power modulalite protector as well. Do I really need to do this if the car has the tow prep package? Can I just using a regular wiring harness and connect to the factory T-connector in the trunk under the storage area? In your video on a 2007 RX350 you show the tech just splicing a regular harness directly into the wiring harness in the vehicle.

asked by: Jack P

Expert Reply:

The RX350 with the tow package is somewhat of a rarity. Since your Lexus has the wiring port in the rear drivers side cargo area, I would recommend using a circuit tester like part # 40376 and check to see if that port is active. Activate the left turn signal, and probe the wires until you locate the one that makes your tester light. Repeat this procedure to identify the right turn and running light circuit. I would recommend also testing the right and left turn wire on the port to make sure you get a signal when the brake pedal is activated. This will ensure that the signal is converted like the lighting system on a trailer. Also check the fuse box under the hood to ensure that the tow package fuse is installed.

If the fuse is installed and the port in the cargo area is active, you can certainly use the # 18002 as shown in the video.

expert reply by: Mike L