1st Gen headlight wiring issue

Hey guys just purchase a 2000 Tacoma V6 5speed 4x4 yesterday. 237k mile and running strong. Only major issue I've found so far is previous owner installed projector headlights with halos. And wired it funky. When I hit the brakes the halos come on and when the headlights are on the brake lights dont work. But brake lights work just fine when headlights are off. Where would you guys recommend starting the hunt for the wiring issue?
Thank you

 

Remove everything that is not oem. Hard to diagnose a problem with someone else’s half assed shit in the way.

 

Fair enough

Thank you

 

Who knows just what might have been done .

How the brake light circuit is involved might be very well be the headlights grounding through the brake light circuit.

I really hope you have the Electrical Wiring Diagrams for Your Truck

 

I dont yet I plan on purchasing the Haynes manual

 

Ekectrical diagrams in Haynes are missing whole bunch of stuff required do do electrical trace. You need real book.

 

What book do you recommend?

 

The only spot that the brake circuit interacts with the headlights or parking lights is at the tail light bulb. It is most likely an issue with the ground at the tail light as well as the way the projectors were installed.

Does your truck have LED tail light bulbs? Does it have aftermarket tail lights? Does it have a trailer wiring harness?

All of these things need to be looked at while you look at the projector headlights.

EDIT: When you hit the brakes and the halos come on, this tells me that the ground for your brake light circuit is bad. Since the ground is bad at the taillights, the power flows through the "parking light" filament (same bulb as brake) and finds the ground at the halos. This is assuming that the halos are wired into your parking lights. You can test this by unplugging your taillights. If the halos don't come on with the brake, you have a problem at your taillight.

The fact that the brakes don't work when the headlights are on could also be related to this bad ground. Look at the back side of each taillight (it's usually on the driver side) for corroded sockets. There are ground wires that are crimped onto the metal sockets, these tend to corrode and fall off.

 

Here are the wiring diagrams for a 1999. There may be some differences with a 2000.

 

So so people know what is the difference between Haynes or Chilton and the real EWD here is the all information what I could find in Haynes for Headlight circuit (scan form the real book).


In general the diagram is correct but missing all information about pin numbers in plugs, connectors and junction boxes. Same diagram in Toyota EDW:



plus all connectors info and reference to other pages where related parts are located.



That's the difference.

 

I wouldn't call what a Haynes manual has as a "wiring diagram."

Get the factory one. You can find them online if you search for them (technically pirated) or get one from a dealer.

 

Hey guys thank you so much for your help with this.

 

So I wanted to update you guys. I started tracing wires and making sure nothing was crossed. You guys are not gonna believe how easy it was. The previous dumbass managed to put the brake light in backwards. As you know it only goes one way. Well he figured it out to make it go the other way. I know @nzbrock mentioned that's where they met but assumed it was installed correctly. Thanks for all the help guys!

 

Glad you found it! Sometimes it's the simplest things that cause all sort of wiring issues.