BLIS & tapping into 4 prong trailer wiring

[Big Blue]

Question for the more knowledgeable. I want to install the same light bar Neilp installed. I am planning to wire differently. I am planning to tap in at the tail lightto the respective wires.

Question is will I still have issues with BLISS and the truck thinking I am towing a trailer? I have a 2021 Lariat with the techknowledgy package.

Thanks for you help.

You can tap into the taillight wiring and not have the truck think its towing a trailer. What you do need to do is use a converter module to combine the brake lights with the turn signals. The module also needs to isolate the lightbar from taillights so the BCM doesn’t see too much extra load. Our trucks have separate bulbs/LEDs for brakes and turn signals. The lightbar expects to see the brakes combined with the turn signals, which is how most trailers are wired in the US.

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[NeilP]

The last few days I got to thinking about a way to out smart the Ranger so that it doesn't think that I have a trailer connected when in fact all that is connected is a multi-function LED light bar connected to the 4 prong trailer plug. Apparently BLIS continues to work as long as I have the trailer setting to no longer than 3 ft., but the sensors in the bumper are disabled and there's no factory over-ride.

Well, I couldn't live with that! So yesterday I took a 5 prong relay out of my parts stash and started tinkering. After figuring out which prongs did what, I temporarily connected the relay to the Ranger and the aftermarket LED light bar with test leads & alligator clips.

The test with the temporary connections appear to successful! So tomorrow I need to pick up a relay plug at NAPA and make this a permanent modification.

Right now I am now a happy camper! My LED light bar seems to work properly and the sensors in the bumper are working even with the light bar plugged in.

 

[Big Blue]

The test was successful! So tomorrow I need to pick up a relay plug at NAPA and make this a permanent modification.

I am now a happy camper! My LED light bar works properly and the sensors in the bumper are working even with the light bar plugged in.

Schematic/diagram please. And what happens when you do plug a trailer in, with this setup?

 

[NeilP]

Schematic/diagram please. And what happens when you do plug a trailer in, with this setup?

Give me another couple of days to play around with this before I do a diagram...I ran into some bumps in the road today.


I edited my earlier post claiming success. I picked up a waterproof relay & waterproof relay plug from NAPA ($60 bucks!) I got it all wired up and started testing it again now that the connections are done properly. Well.......apparently the new high dollar relay is defective. If I wiggled it or bumped it, I'd lose an internal connection. Replacement relay is on order.

BUT, I was able to test it a bit more as long as long as I didn't move the relay and I learned a few things that were disappointing, but it makes perfect sense. Everytime I would shift into reverse, the display would momentarily issue a "trailer disconnected" warning. When shifting out of reverse, the display would indicate "trailer connected". However the light bar and reverse sensors still seem to be working like I was hoping.
I'll know more after the new relay shows up. I am hopeful all will be well. If not...lesson learned.

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