My 2000 SR5 4x4 keeps blowing the tail light fuse. I thought it was the brake switch but it tests good. I've replaced all the brake lights and check all the wiring for any chaffed areas. The brake lights work fine in park and I can feel the brake lock solenoid going in and out. As soon as I shift out of park with my foot on the brake the fuse blows. Could it possibly be the brake shift computer?
Keep blowing brake light fuse
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spartacus
Senior Member
There is an interlock solonoid that gets power to release the shift lock. Trailer wiring controller or plug corroded. Check the wires in the rubber boot for the wiring to the hatch. 3rd brake light bulb contacts corroded, if you've already checked the brake light holders for corrosion.
brillo_76
Elite Member
Sounding to me like a dead short in the stoplight circuit. If it's shifting out of the interlock for park the brake switch is working. I suspecting a broken wire in your 3rd brake light as well. Or it's shorting against ground blowing your fuse.
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Sent from my SM-A505U using Tapatalk
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RAD4Runner
Senior Member
A problem well-stated is a problem solved.
Care to clarify what is really blowing? Brake light fuse as in your post title, or
tail light fuse as in your description? Those are two different fuses supplying different circuits.
Do you have daytime running lights? Does problem occur whether engine is running or not?
Care to clarify what is really blowing? Brake light fuse as in your post title, or
tail light fuse as in your description? Those are two different fuses supplying different circuits.
However, title says "Keep blowing brake light fuse"
This step ^^^ turns on daytime running lights, IF you have any.
Do you have daytime running lights? Does problem occur whether engine is running or not?
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Sorry for the confusion. It's only the brake light fuse that keeps on blowing when I shift out of park with the engine running and my foot on the brake. And yes, I have daytime running lights.
I have the entire back of the car opened up to access the wiring. I've checked everything I can get to and I've replaced all three brake light bulbs. When I'm in park with the engine running, I tap the brake and all three brake lights illuminate and I can hear and feel the shift solenoid moving in the shifter. I then move the car out of park and I can hear the brake light fuse blow.
The brake circuit is separate so why is the brake light fuse blowing when I move out of park into reverse which is not part of the brake light circuit?
Question - On the inside of the left rear quarter panel is a black box about the size of a deck of cards stuck to the inside of the quarter panel. It has wires going into the top and out of the bottom. I can't find anything that tells me what it is.
Could it be that there's a short in the neutral safety switch?
I have the entire back of the car opened up to access the wiring. I've checked everything I can get to and I've replaced all three brake light bulbs. When I'm in park with the engine running, I tap the brake and all three brake lights illuminate and I can hear and feel the shift solenoid moving in the shifter. I then move the car out of park and I can hear the brake light fuse blow.
The brake circuit is separate so why is the brake light fuse blowing when I move out of park into reverse which is not part of the brake light circuit?
Question - On the inside of the left rear quarter panel is a black box about the size of a deck of cards stuck to the inside of the quarter panel. It has wires going into the top and out of the bottom. I can't find anything that tells me what it is.
Could it be that there's a short in the neutral safety switch?
As I said, I replaced all three brake light bulbs. The 3rd brake light socket look like it had gotten hot because the white plastic was a light brown color but the socket looked ok inside. I unplugged the socket at the connector and it still blew the fuse. The other brake light sockets looked fine.
I don't think I can shift out of park without the engine running. Kind of hard to test right now.
I unplugged the two large connectors in the ceiling of the cargo compartment to the left of the cargo light. None of the rear lights worked anymore and when I started the car and shifted out of park with my foot on the brake the fuse did not blow.
I have stock trailer wiring. Several months ago I rented a trailer to bring home a new Harley. Could something have happened to the trailer circuit? The plug looks fine.
I don't think I can shift out of park without the engine running. Kind of hard to test right now.
I unplugged the two large connectors in the ceiling of the cargo compartment to the left of the cargo light. None of the rear lights worked anymore and when I started the car and shifted out of park with my foot on the brake the fuse did not blow.
I have stock trailer wiring. Several months ago I rented a trailer to bring home a new Harley. Could something have happened to the trailer circuit? The plug looks fine.
brillo_76
Elite Member
You can unplug the trailer harness box to rule it out. The stock one is in the driver side behind the big plastic panel near the real tail light. If aftermarket, they are on the passenger side tail light as mine oem blew and the aftermarket is the opposite tail light.
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I had a similar problem and, like others here, found that the factory trailer light "multiplexer" was the faulty component. Mine had visibly distorted due to heat of an internal short. I recalled when I diagnosed the problem that a week or so earlier I'd smelled "hot plastic" while driving.
The OEM item is, to my knowledge, NLA and was quite expensive when it was still available. That it is NLA might speak to its frequent replacement.
I replaced it with a Hopkins 43415 kit. Amazon has 'em for $48.64. Mine has been working for over 10 years.
Perhaps replacing the OEM item with a Hopkins could be seen as a reasonable prophylactic measure.
The OEM item is, to my knowledge, NLA and was quite expensive when it was still available. That it is NLA might speak to its frequent replacement.
I replaced it with a Hopkins 43415 kit. Amazon has 'em for $48.64. Mine has been working for over 10 years.
Perhaps replacing the OEM item with a Hopkins could be seen as a reasonable prophylactic measure.
phattyduck
Elite Member
I've had TWO OEM trailer light boxes go bad... Maybe even a third when my dad had it. Now on an aftermarket from etrailer (can't remember the brand).
-Charlie
-Charlie
I finally found the problem. It was the tailgate wiring where the tailgate hinges. The big black wire was almost broken through entirely. I repaired the black wire where it was broken and I cut the others close to the connector and slid a piece of shrink wrap to where the insulation was broken. I didn't want any more wire splices close to where the door hinges.
Thanks to all for the help. Just talking things through with someone really helps sometimes. Kudos to Spartacus for suggesting the hatchback. I just started eliminating wire branches by disconnecting things until the fuse no longer blew. What threw me was everything worked fine until I shifted out of park into reverse. I'm still not sure how the hatchback wiring has anything to do with the backup circuit.
Anyway, it's fixed now and my wife is happy. The car only has 115k on the odometer and it's been perfect until this issue. Fortunately, I could fix it myself with a little help from my friends and toyota-4runner.org.
eace:
Thanks to all for the help. Just talking things through with someone really helps sometimes. Kudos to Spartacus for suggesting the hatchback. I just started eliminating wire branches by disconnecting things until the fuse no longer blew. What threw me was everything worked fine until I shifted out of park into reverse. I'm still not sure how the hatchback wiring has anything to do with the backup circuit.
Anyway, it's fixed now and my wife is happy. The car only has 115k on the odometer and it's been perfect until this issue. Fortunately, I could fix it myself with a little help from my friends and toyota-4runner.org.
eace:Attachments
SLOrunner87
New member
brillo_76
Elite Member
The Hopkins units will work. However,they can burn out too. I just lost the driver side turn signal out of mine..
if it's the same kit I got it will hook into the passenger side instead of the drivers side. So wiring will have to flip. Sent from my SM-A505U using Tapatalk
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