Brake Light Issue
 

Looking for some insight on a slight issue I am having, my brake lights are no longer working, the odd thing is I can turn on my headlights and they will all illuminate, including the 3rd brake light, when the brake pedal is not even being used.

I know there can be brake light issues when replacing bulbs and using the wrong count filament, not the case in my situation. Based on a few posts I was able to dig up, the likely culprit may seem to be a faulty wire, those same posts also mentioned it would likely be a major pain to track it down.

The other thing throwing a wrench in the plan is that I just recently had the front calipers replaced, the rear brake shoes replaced, and the e-brake adjusted, I am thinking this is just a coincidence, but is there somewhere I should be looking where this work was completed that may effect wiring?

Ultimately, if faulty wiring and will require an electrical engineering degree to find, I will more than likely disregard as the vehicle stays offroad and on FS areas. Outside of the obvious safety issue, would there be any other worries mechanically if disregarding.

Another thing I might mention, I have the Andy Mod wire cut, not wired to a switch, to where ABS and VSC are permanently disabled, could there be an issue there?

Any thoughts are appreciated.

2001 4 Runner SR5

Dash lights work (main dash lights not so much the individual warnings lights)? Front marker lights work? Both are on the same circuit.

Guessing you checked the fuse for continuity?

I don't think the other things you've done are related.

A 'bad' wire usually shorts out, hence checking the fuse first....

All other lights work, I ran it through the car wash yesterday and wife brought it up when she was behind me on the way home, it was already late so I have not pulled any fuses yet but would think it odd if a fuse was blown. I would think they would either work or not, not work when the headlights are turned on. Will dig in deeper and definitely check fuses when I get home this evening, just sitting at work now thinking heavy and hoping there may be something obvious out there that I am ignorant about or failed to find searching. Thank you.

Could be a dirty ground loose wiring rusty socket. Test the socket pins should have 12 volts Have some one step on the brakes and check.. Turn your hazards on and see if they work I believe they use the same filament.

White/Black- Ground
Green- Running lights
Green/White- Stop Lights

edit: Just noticed you have 2001. There was a change in the tail light harness in 01 and 02.

Courtesy of @TheDurk . the tail lighthe wiring 2001 4runner.

Does the shifter come out of Park correctly when the brake pedal is applied? Does the cruise control cancel when you press the brakes? Same two questions, but with the head lights turned on?

Are the brake lights full brightness when the headlights are on, or are they dim?

I think step 1 is finding and unplugging the trailer light adapter. I think on the 01/02's it is a factory installed thing behind the driver's side trunk panel.

-Charlie

Not saying you are negligent, but it is possible both brake bulbs are just burnt out. One filament can work and the second can go out which makes it look like the bulb is fine, but won't illuminate when you press on the brake pedal. It's only about $5 to rule that out before you start chasing wires. Also, might be good to just replace the fuse for the brake circuit or swap it with another fuse that's good on the fuse box.

Oh this is great, I hope I don't have to use, but will be perfect to reference if chasing.

Shifter release is permanently stuck in contact due to the VSC/ABS being disabled. Will test cruise control tonight when I get home. They are bright as can be when the headlights are on, no dimness, no flutter. Interesting thought on the trailer adapter, read an older post where someone had issue with their trailer plug causing gremlins, symptoms were a bit different, will be easy enough to disconnect as I will never use this vehicle to haul.

Fair assessment, bulbs def. are not burned though, the brightness is overly obvious that brake lights are illuminated, like you said though, cheap and easiest before digging through the electrical diagram provided. Will give it a go to test along with new fuses, worse case I have known new components there.



Thanks for the thoughts, does not seem like it could be a more detrimental issue causing this, appears that it will be directly related to the wiring, bulbs. As much stuff that has been done to this vehicle previously, my mind gets to wandering on how basic issues can blow up or be underlying nightmares.

Alright, got it figured out. Running through all the things that were brought up above, while getting ready to pull my bulbs I noticed a wire coming out of the right rear housing. This wire is what use to power the license plate light (which also included a three light brake light) on my tire carrier bumper. While wiggling it I noticed the brake lights would cut on and off.

At this point, I am thinking this is going to be an easy fix, I care nothing about a license plate light so I just trim the wire behind where it is making the bad connection and coil it neatly into the housing. Try the brakes and nothing, turn the lights on and now it is just the tail lights illuminating as you would expect, brake lights no longer permanently on.

Check the fuse, and sure enough, when I trimmed the wires, I blew it. New fuse and good as new. Easy fix, thanks for the advice, updating in case anyone else has the problem, ended up being faulty wiring in aftermarket lighting that made a constant connection due to brake light being tied in with the tail light wire that powered the license plate light.