Probably a short in the tail lights some where.

 

Had a very similar problem in my 88 Cherokee. It was a bad ground at the light assembly.

 

What did you have to do to repair it? Was it as simple as removing the light and re-attaching the grounding wire?

 

Odds are that the brake light hot wire is shorted. When you hit the brakes it lights up the turn signal. You will have to find the break and repair accordingly.

Dose your truck have an aftermarket trailer wire harness?

 

Had a very similar problem in my 88 Cherokee. It was a bad ground at the light assembly.

I will bet you are right. The only thing that those two systems have in common is a common grounding point. If the ground is bad, one system can back feed into the other looking for a ground and cause symptoms like the poster described.

Gadget

 

If your brake light hot wire was shorted to ground you would be popping fuses.

As far as the repair, I had to disassemble the turn light assembly and resolder the ground wire to the lamp holder. Yours could be as simple a dirty ground contact at the bulb. If the contacts are clean you will have to check the ground wire from the bulb holder to its body or frame grounding point. Unlike most american cars, most Japanese and European cars have turn signals that are independant of the brake lights (hence the seperate amber lights) and the only place the 2 systems meet is in the ground circuit. This is the reason that you need an adapter box to wire most Japanese and European cars to tariler that have a simple 2 light set up.

 

If your brake light hot wire was shorted to ground you would be popping fuses.

A short will only blow a fuse if the load is sufficent to blow a fuse; such as when a hot wire is shorted direct to the body. If it is shorted to the blinker ground then the voltage back travels through the bulb, or if it is shorted to the blinker hot then it turns on the bulb. Broken or dirty grounds don't cause lights to come on; they cause lights to not come on. If the ground is broken then the circut is open and power can't flow. No power=no lights.

 

Yes, if a ground is disconnected there will be no circuit completion, but a poor ground such as a loose connector or corroded contact will cause all sorts of weird problems becasue the ciruit then looks for a ground elsewhere. One of the symptoms is having an interior signal light illuminate when it should not. If it were shorted to blinker ground it will still blow a fuse as the light, blinkers included, ground to chassis or body. They do not ground through the switches. If you are shorting to ground you are shorting to ground reguardless of which ground it its - you are bypassing the resistance load (in this case th ebulb) designed into the circuit.

 

Thanks for the help. I will start the trouble-shooting process soon. I will let you know what I found. Thanks again.

 

Also, I am not certain if it is an after-market wiring harness. I bought the truck from a dealer (I am the 3rd owner). The previous owner bought it as a certified vehicle from a Toyota dealer.

 

I had the same problem. It was in my trailor hitch wiriing. Some kind of short in the after dealer installed trailor wiring. It was a while ago so i forget details but if u have one check it.

 

This symptom can most certainly be caused by a loose or disconnected ground wire for the taillight assy. Try hitting the brakes with the taillights on. If the taillight dims or goes out then check grounding. The "it must be a SHORT responses should be ignored!!

 

I Had The Same Probelm With My 2001 Tacoma. I Eliminated The Problem By Removing The Aftermarket Wiring Harness That Was Spliced Into My Tail Lights And Bought A Harness That Plugs Directly Into The Tail Lights.

 

What type of wiring harness would you recommend? Is it a difficult change?

 

What type of wiring harness would you recommend? Is it a difficult change?

I BOUGHT MY WIRING HARNESS FROM WAL-MART IT'S THE CUSTOM FIT TYPE. I THINK HIDDEN HITCH MADE IT. IT WAS VERY SIMPLE TO INSTALL JUST REMOVE YOUR TAIL LIGHTS, UNPLUG THE FACTORY TAIL LIGHT WIRES, PLUG IN THE TRAILER HARNESS TO THE TAIL LIGHTS, THEN THE FACTORY WIRES TO THE TRAILER HARNESS AND TIE UP THE WIRES FROM THE HARNESS WITH CABLE TIES SO THEY ARE NOT HANGING UNDERNEATH AND YOUR DONE.