2023 Lexus RX 350 Premium - OEM trailer wiring

[Ucandobetterlex]

Hello to all,

Any thoughts on this greatly appreciated.

I have a 2023 Lexus RX 350 premium - Looking to tow a small boat or trailer.  Purchased the Lexus OEM wiring harness from the dealer. Plugged in and routed wires no issues.

Tried to test the 4-pin connection on a harness tester and a known working trailer, turn signals, brakes, ect.  No power to the lights.  Checked the harness wires for continuity and trailer fuse under the hood and no issues.

I was under the impression from a previous forum thread the OEM wiring harness was plug and go.   Any thoughts on what I may be missing or should check would be greatly appreciated.  Thanks...

[RX400h06]

5 hours ago, Ucandobetterlex said:

Hello to all,

Any thoughts on this greatly appreciated.

I have a 2023 Lexus RX 350 premium - Looking to tow a small boat or trailer.  Purchased the Lexus OEM wiring harness from the dealer. Plugged in and routed wires no issues.

Tried to test the 4-pin connection on a harness tester and a known working trailer, turn signals, brakes, ect.  No power to the lights.  Checked the harness wires for continuity and trailer fuse under the hood and no issues.

I was under the impression from a previous forum thread the OEM wiring harness was plug and go.   Any thoughts on what I may be missing or should check would be greatly appreciated.  Thanks...

Quote

It sounds like you've done a thorough check already, but here are a few things you might want to consider:

1. Check for a Separate Activation Step – Some OEM wiring harnesses require activation through the vehicle’s onboard computer or a fuse relay that needs to be manually engaged.
2. Verify Ground Connection – A weak or missing ground can prevent power from reaching the trailer lights.
3. Confirm Power at the Connector – Use a multimeter to check if voltage is reaching the 4-pin connector when the vehicle’s lights and signals are activated.
4. Inspect for Hidden Fuses or Relays – Some vehicles have additional fuses or relays specifically for trailer wiring that may not be immediately obvious.
5. Look for Software Updates – Some Lexus models require a software update or dealer programming to enable trailer wiring functionality.