1997 toyota 4runner left turn signal indicator is dimly lit when i press the brakes

Check for wires being pinched by the brake pedal arm.

Sounds like a ground problem to me. Bulbs are not getting there ground to complete the circuit so they backfed through the other bulbs.

{: ) Looks like your lightings got haywired. Have you had vehicle repairs recently? Anyway, it seems that you have poor grounding connections for the affected lightings. Some circuits share common ground, and ground terminals are strategically distributed on the vehicle. If these grounds don't have good contact with the body, chassis, or engine ground, circuit functions are badly affected. Thats why these ground points should be inspected and kept clean and tight, maintain that good wire and terminal contacts.
We can start with G100 located at the Left Front of the Engine Compartment on the left front body mount. See diagram below:


Check out also G401 which is located in the chassis harness, mounted to the left rear Body mount. This ground point is shared by the rear lamps like the brakes, reverse, and rear signal lamps.
If possible check also other ground points that you may visually come across while on your search. Be sure also that fuses are all inspected good.
I hope we get lucky in finding and fixing a certain lamp function, if not all. Goodluck.

Lots of possibilities, but the most common is a bad ground of the entire light assembly on the left rear.
That makes the left rear brake filament ground back up through the left rear turn signal ground, through the left rear signal filament, and all the way back up to the dash left indicator light, then finally to chassis ground. Just check if the left brake and left signal are both dim and come on together.

either a stop or turn signal or tail lights are out

sounds like you may have a bad brake light switch i think you problem will go away if you change it out. hope this has been of some help to you !

Sounds like the jolt from the barrier has caused a bad ground to occur. Look for a bad ground wire around the left headlamp in or around the headlight bucket.
Tighten or replace the bad ground wire. A poor contact will cause the headlight to light dimly.

The trailer harness that was installed probably has a short inside the box that distributes power to the trailer pig-tail. Remove the trailer harness. You problem will be cured.

you have a back break light out

Igot the same problem on left side.The problem was the convertor for the trailler plug.