Trailer lighting issues

Good day to all my Taco brothers and sisters, I'm new here and in search of an electrical guru, I have a 2015 Tacoma TRD Off Road with a 5X8 trailer lighting concern, when the trailer is connected to the truck and the trucks lights are off, all trailer lighting is working as designed, stop, turn signals, when I turn the truck lights on right trailer tail light is bright and left is dim no turn signals work but the truck lights work as designed??? did my due diligence checked grounds and power, and all truck fuses fyi trailer is newish wiring looks good.

 

Have you tested the pins on the truck side with a DVM to verify that the V is correct when a pin is activated?

 

Thanks for the quick response, yes I have 12v across the board, I failed to mention it's a 5 wire harness with 4 flat pin connector, trailer side.

 

So when you use the left signal, that pin flashes 12v, correct? And the other 3 are 0v if running lights are off. Etc etc.

And all pins test operationally that same way?

If that's the case, it seems the trailer is where the issue is.

 

That is correct, now I just thought of this, I have an aftermarket grill with led lights which I tapped in to the left parking light (so it wouldn't blink if I tapped it in to the drl) could his be the issue

 

Is that with an aftermarket taillight converter, as opposed to the factory tow hookup?

 

It would almost have to be?
OE is 7 pin.

Some dealerships would add a 4 pin.
But a 5 pin? Never seen that as an option from any dealership.
5 pin is basically a 4 pin +Reverse Light.

 

I was just trying to clarify that it was indeed the case... and not, like, "I'm using a 5-pin adapter/cable from the 7-pin" cuz not everyone always types things clearly.

Cuz my experience with taillight converters from having a 1st gen is... they all suck, and they all fail, and they often fail in weird ways. I think I had 6 or 7 of them on there over 15ish years.

From what OP described, I'd peg it as either a bad ground or bad converter, and I'm not having luck picturing in my head how the bad ground could do all those things (working fine without HLs, no turn signals with HL, and the single stoplight instead of taillight)

 

I agree.
Those after market converters are more trouble than they are worth.

 

Unfortunately I don't know of a (plausible) better way for something like a 1st gen, with separate turns & tails, and no factory support for a trailer.

But I damn sure don't miss it with my factory tow package now!