In the floor cover behind the drivers seat (turn the knob on the cover & lift it out)
you'll see some inline fuse holders in the wiring harness........... one of them is the trailer brake lights
Good Luck !!!
On a toyota tacoma 2003 SR5 when the tail lights are turned on the brake lights come on and when the tail lights are of the brake lights work just fine what could be the problem. If the truck has a trailer plug, inspect the plug and plug wiring for damage and corrosion.
Yes
Your trailer tailights are dual-filament, with one being the running lights and the other the brake lights. You need a separate power source from your towing vehicle's brake lights to power them. The easiest way to do this is go to U-Haul and but a set of their trailer towing taillight bulbs for your towing vehicle. The bulbs replace your standard tail/brake light bulbs, and they have two wires coming out of the base of the bulb. One of the wires connects to your trailer's running lights, and the other one connects to your trailer's brake light circuit. I'm trusting that when you re-wired your trailer, you ran two wires from the taillight socket, one for the running lights and one for the brake lights. In some trailers, the brake light circuit also doubles as your turn signals. Good Luck.
There are no extra fuses for your trailer lights. If you have the towing package (and you do) the trailer lights run through your regular fuses (tail, brake, turn).
I would check the running lights for one with a short. I had the same sort of thing with my trailer and I spent way to much time troubleshooting the brake and signal wires. Turns out a running light bulb connector was grounding out on the trailer and messing it all up.
there may be a short get longer wires
every vehicle must have brake lights to indicate that the vehicle is stopping. with no brake lights the vehicle can cause a rear end collision.
Tail lights and brake lights fuse.
You have a poor or no ground between the vehicle and trailer.
short circuit on trailer light wiring
The brake lights
The brake lights