Trailer harness running lights only working

hello all,

New to the forum. Great info here. Anyway, towing my boat and noticed my brake and signals not working. Put a multimeter to the harness and only get 12v from the running lights and nothing from from the brake turn signal. Please help truck is 4 months old. Dealer needs all day they say. “Could be rodent”.

Thanks in advance.

 

Can you crawl under your truck and see if any of the wires are chewed up?

 

No wire chewed up. Everthing looks good. I wonder if anyone has the wiring schematic.?

 

Possibly a fuse..??

 

USE YOUR WARRANTY!!!!

G.

 

All fuses are working. Dealership is giving me the “ it might not be under warranty if a pest chewed some wires”. I am bringing in Wednesday. They said they need all day with it.

 

I have a cheap tester that checks the plug (connector) at the rear of the truck. Plug in and run your normal checks for running lights, brake, signals, power (7pin). In my experience it is usually the tow harness on the trailer that has lost a ground or other connections. Rarely is it the truck harness unless a fuse has blown (or a dodge which blows the unserviceable towing only flasher every 2 years).

Check online for the tester I am speaking of. It is a huge time saver.
Edit:
https://www.etrailer.com/Accessories-and-Parts/Tow-Ready/TR20117.html
No this won’t void your warranty (you really think this is screwing with your truck?) but if you go to your dealer and the issue was your trailer I suspect they will charge you shop rate for their time. Best to eliminate the trailer first.

 

The tester is a good idea. However, if it's an issue with the brand new truck, don't give Toyota a reason to say "you screwed with it, so it's your problem". If it is rodents, well, then that sucks and can be very expensive.

Keep us posted.

G.

 

Get a test light and check for power at each pin. If you have power at rear of truck -- it's most likely your trailer ground or wiring.

 

Check the ground connection on the trailer, with some trailers I've used a jumper wire with clamps from truck frame, to the trailer frame.

 

wiring schematic

 

Stop by a U-Haul place and see if they will let you hook up to one of their trailers.

G.

 

/pickupman2007 thanks for the schematic. There is no power going to the back of my trailer harness on my truck except for running lights. Check them with a multimeter.

 

I noticed a wiring clip by the driver side fuse box that isn’t plug in to anything

 

Did you check all your fuses?

If you checked the plug on the back of your truck without a trailer plugged in and there's nothing there, I don't see what it could be other than blown fuses or damaged wires.