Brake lights constantly on? - Toyota 4Runner Forum

rwh963 · 02-21-2022, 12:18 PM

recently i've had a couple of people tell me my brake lights are constantly on while i'm driving. haven't had time to check on it, but wondering, if true, what would be the issue is there a stuck plunger/contact/sensor?

OopsIBrokeIt · 02-21-2022, 12:32 PM

95% chance your brake light switch has failed.

Replace it and you should be back to normal.

rwh963 · 02-21-2022, 08:25 PM

nighttime. decided to test the brake lights. turn on ignition, brake lights are on (don't recall if third light is on). pulled the switch, worked the plunger, seemed to work properly with ignition off. put switch back in, worked normal with ignition off. so, switch works normal with ignition off, not so with ignition on.

Bl4ck4rm4 · 02-21-2022, 09:40 PM

Here is another option, there is a green tab on your brake pedal arm, check to see if it is there? Or feel with your hand where the brake switch meets the brake pedal arm. It is a plastic piece that is notorious for breaking. Most Asian cars have them and they break. You can get a replacement, which cost about 8-15 buck that will eventually fail again or a cheap fix of a coin, penny or nickel and tape it in place for a temporary fix. I have fixed these in Toyotas, Lexus, Nissans and Honda.

Check your floor mat for green pieces.

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Jakeepoo3 · 02-21-2022, 10:38 PM

Clean and check for correct gap. Check voltages and continuity with multimeter. Look at stop and ign fuses.

AudiQU4TTRO · 02-21-2022, 10:50 PM

Let us know what you find.

I have seen this issue quite a bit and usually its just the brake light switch under the brake pedal. You may be able to get under there and just wiggle the connector for them to go off, but they will still work. Just won't be on constaly.

Hopefully its something simple like that.

Bl4ck4rm4 · 02-21-2022, 11:08 PM

Quote:

Originally Posted by rwh963

nighttime. decided to test the brake lights. turn on ignition, brake lights are on (don't recall if third light is on). pulled the switch, worked the plunger, seemed to work properly with ignition off. put switch back in, worked normal with ignition off. so, switch works normal with ignition off, not so with ignition on.

I’m assuming when you pulled the switch, you still had it connected with the wire harness. If it worked when you tried it and was fine ignition off, good. You placed the switch back to its original location it was fine. You start the truck the lights come on.

Do the tail lights stay on after you shut down the truck?

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rwh963 · 02-22-2022, 10:12 AM

yes, switch was still connected to to the wires. so, switch works like this: brake pedal off, plunger depressed. press brake, plunger released, brake lights go on.

with ignition off, switch worked normal. with ignition on, brake lights constantly on weather brake on or off. must be something faulty in the switch. original, with 230k miles. i can grab one for $30 at the dealer. i'll try that route.

rwh963 · 02-22-2022, 10:15 AM

Quote:

Originally Posted by Jakeepoo3

Clean and check for correct gap. Check voltages and continuity with multimeter. Look at stop and ign fuses.

wow, thx for that. i think the fastest way to check is to grab a new one for $30 and see if that corrects this issue.

Jakeepoo3 · 02-22-2022, 11:53 AM

Quote:

Originally Posted by rwh963

wow, thx for that. i think the fastest way to check is to grab a new one for $30 and see if that corrects this issue.

No problem. I may have misunderstood your post I reckon. The switch activates and deactivates via ignition switch without touching the pedal. Possibly the contact or spring is at fault..

rwh963 · 02-22-2022, 03:24 PM

normally i don't think about how the brake lights function. if i'm sitting in there car without the ignition on and have my foot on the brake pedal, the lights do not come on?

rwh963 · 02-22-2022, 03:28 PM

update: picked up a new switch at the dealer. installed it, same issue. turn the car on, brake lights (all three) go on. annoying. maybe the brake pedal needs adjusting. perhaps the switch plunger is not going down far enough.

Jakeepoo3 · 02-22-2022, 03:49 PM

Quote:

Originally Posted by rwh963

update: picked up a new switch at the dealer. installed it, same issue. turn the car on, brake lights (all three) go on. annoying. maybe the brake pedal needs adjusting. perhaps the switch plunger is not going down far enough.

Do you understand the diagram of the circuit the switch is on that I posted? It tells you everything you need to know. I would have told you it probably wasn't the switch since it was actually working but kind of in reverse. It literally takes a couple minutes to test it for continuity while pressed and depressed that would have saved time and you buying parts. Notice the circuit includes a relay that interacts with the stop switch when the ignition is turned!! 😉😉 Do you have a multimeter and a test light. They cost less than parts and you can diagnose pretty much anything with 15$ in simple tools. Most the time it's not even the part but something simple within the circuit.

rwh963 · 02-22-2022, 04:03 PM

Quote:

Originally Posted by Jakeepoo3

Do you understand the diagram of the circuit the switch is on that I posted? It tells you everything you need to know. I would have told you it probably wasn't the switch since it was actually working but kind of in reverse. It literally takes a couple minutes to test it for continuity while pressed and depressed that would have saved time and you buying parts. Notice the circuit includes a relay that interacts with the stop switch when the ignition is turned!! �� Do you have a multimeter and a test light. They cost less than parts and you can diagnose pretty much anything with 15$ in simple tools. Most the time it's not even the part but something simple within the circuit.

no loss of time and money. was going by there anyway, and can return it without an issue, even though it was only $30 for a switch that has been used many times over the last 230k miles, sop maybe i'll just keep it.

it literally may have taken you a couple of minutes, but i'm not familiar with the procedure, so first time usually takes longer.

i do have a multimeter (and possibly a test light).

"something simple within the circuit": care to share what you're thinking?!

Jakeepoo3 · 02-22-2022, 05:11 PM

Quote:

Originally Posted by rwh963

no loss of time and money. was going by there anyway, and can return it without an issue, even though it was only $30 for a switch that has been used many times over the last 230k miles, sop maybe i'll just keep it.

it literally may have taken you a couple of minutes, but i'm not familiar with the procedure, so first time usually takers longer.

i do have a multimeter (and possibly a test light).

"something simple within the circuit": care to share what you're thinking?!

I understand. I learned the first time also. It pays off big time! First check the fuses I circled visually. There is a relay that I suspect is the issue circled. You can test it with the tools I mentioned if you like. Do you hear a click with the ignition on but not started when you touch the pedal? That's the sound of an energized relay. That doesn't mean its not bad but you can test it further like I said. Use a test light or multimeter to check for battery voltage at the stop switch and check your ground there also with test light. Power to ground. Use the diagram to find the proper terminals to test. Hollar back young one!

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