3rd Gen Trailer Left and Right Turn signals/brake lights not working

I tow a lot for work and recently noticed the turn signals/brake lights that used to work quit working. Problem is definitely coming from the truck (4 trailers do the same thing, a different truck runs all trailers properly).
Checked all fuses/relays labeled for towing u see the hood and under the dash. A shop also looked at it today and couldn’t figure it out. Trucks signals/ brake lights work just not the trailers. All trailer running lights work

 

Probably corroded contacts

 

Have you tested the 4 pin and the 7 pin for their output? They are internally connected at the tailgate output (T12)

 

Not sure about 3rd gen but 2nd gens use a trailer light module to convert trucks separate brake/signal light outputs to common output.

 

3rd Gen has it integrated as part of the Combination Meter (Gauge Panel)

 

Both the 4 pin and 7 pin has no turn signals

 

And STOP is also missing from both?

 

Verify circuits as you have for the towing connector, at the engine bay fuse/relay box, connector EB3-pins #5 & #16.

 

Just had it at Toyota. They’re charging me $70 and didn’t even fix it. They blame my after market lights wiring as reason for not wanting to mess with it

 

Turn signals/brake lights are connected. Yes STOP doesn’t work on either 4 pin or 7 pin

 

Damn dealership and their petty reasons. Have you verified connector EB3 for power?

 

Toyota claims to have checked those. I don’t have a multi meter but I will check it when I get my hands on one

 

If you have a spare bulb and some wire, assemble a "test light".

 

One thing I failed to mention that I will try next… my friend used his multimeter to check the bumper end of the wires and said the turn signals were throwing over a million volts. I wonder if it can be the dual battery kit I installed? Maybe it’s giving it the wrong amount of power?

 

Maybe you should get a skilled friend...

 

Update on the repair.
Problem was tracked back to the instrument cluster. If anyone could explain how that is related to the trailer turn signals/brake lights that would be great!
Any ideas on how to prevent this from happening again? Inline fuse on the trailer wires?

 

The trailer converter is integrated to the Combo Meter. Takes turn n stop circuits to trailer wires. 2nd Gen has this towing converter as a separate module. Not so for 3rd Gens.

 

What was the exact issue. I tow occasionally and im having the same problem running lights taillights work but no brake or turn signals

 

I'm having the same problem with my gen3 Taco. I just bought a new trailer light set after having replaced them a year ago and found they don't work either. The Hopkins instructions indicate needing an electronic turn signal converter. When I went online and enter my vehicle info there were none that fit my truck. I now know why. it's integrated at the dash/Instrument panel. Is it a reasonable DIY project changing the module at the dash? What did the dealer charge to replace? I HATE going to the Toyota Dealer they always want to make the bill over 100 by finding a wiper blade and cabin air filter to pass inspection. Oil Changes end up being a 100.