Flat Tow Wire Harness Mystery

[RangerD]

Just installed a Blue Ox 4 Diode taillight wiring kit (BX8848) so I can tow a 2025 XLT behind my coach. Four wires run to the back of the truck for left turn/brake, right turn/brake, parking (routed to both lights) and ground. Two diodes are installed on each taillight on the turn/brake and parking light circuits. When I turn the coach parking light on, only the side markers on each taillight illuminate. The rear facing LEDs do not light up. There is only one wire on the body harness (pin #10) that powers both the side marker and rear facing lights. Blue Ox was unable to help.

Has anyone experienced this or know what could potentially cause this?

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[MasterCylinder]

Check your wiring, pin 10 on tail light assembly is Park light and license light I think. Pin 1 and 2 are the stop tail light. I don't have access to my diagrams right now but can send later if you need it. Hope this helps!

 

[Duoglide]

I gave up. I did not want to splice and add diodes to some and not to others. Ford used led and incandescent both on this. I went to iTool.com and got wireless setup. I screwed the metal plates to my roll n lock for magnetic lights. The transmitter plugs into trailer plug on towing vehicle. The lights are rechargeable with usb cord. I’ve towed 4-5 trips so far and no issue. The ones etrailer sells you need a case of batteries to go anywhere. It worked for me.

 

[dajo]

That is why I completely bypassed the Ranger wiring. I ran a completely separate wire to the rear of Ranger and used magnetic lights.

 

[Happycarz]

RangerG, I experienced taillight side markers illuminating with no rear taillight, two months ago when wiring mine.
Only one wire enters the taillight assembly for both the rear and side bulbs. What’s with that?!
Thank you for verifying I'm not nuts.

 

[RangerD]

Thank you for everyone's replies. I verified the pin location for the parking lights against the chart below and by using a test light. Double checked my wiring and tested the diodes to ensure everything functions correctly. Interestingly, with the truck parking lights on, pin 10 lights up my test light clear and bright as expected, but pin 2 has a faint glow almost as though there is a stray voltage. Pin 2 lights up when the brake is applied. Does this stray voltage somehow play a role in lighting the rear facing parking lights? I'm not sure where to go from here.

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