Troubleshooting No Trailer Lights With New Wiring on 2015 Lexus RX 350

Updated 12/26/2019 | Published 12/25/2019

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Question:

I installed the harness behind the driver side bumper. There was already a fuse in the Tow slot, but no fuse inn the Tow Battery slot, di I added poker. Still working. Do I need a tow converter? Thanks.

asked by: Clifford Z

Expert Reply:

Not necessarily. If your 2015 Lexus RX 350 came with the tow package then you just need the T-One # 118252, but if it doesn't have the tow package then you need the T-One # 118255 with the converter. The tow battery fuse slot would only be used if you were installing a 7-Way. Since the connector for the lights just have 4 pins for the trailer lights and ground I don't think it will really matter if you have a fuse in the tow battery slot or not.

Before purchasing a wiring kit with the converter, try using a circuit tester like part # PTW2979 to ensure that power is getting to the plug on the driver's side bumper that you found. If no power is getting to it then you might need the converter. If you are getting power to it then the wiring you received might be defective and you'll want to inspect it for any places where it might be damaged.

Since the problem is that your trailer lights aren't working the problem could be on your trailer side as well. If you're getting power to the 4-Way harness when it's plugged in (which you'd verify with the tester) then you'll need to check all of your connections and grounds on your trailer side to make sure that everything is secure and undamaged.

expert reply by: Jon G