Fog Light Mod
After I installed my OEM Fog Lights I was disappointed that I could not turn them on with just the parking lights, and they automatically shut off when I hit the high beams. Again I searched the net to find a solution. I found two ways to change the operation of the fog lights.
1. What I call the "factory finish method". This entails making a wire change inside the engine bay's fuse box which makes the modification totally hidden. A wire change at the DRL relay assembly is also required for vehicles equipped with DRLs. This is the method I used as it has more of a factory finish.
2. What I call the "quick and dirty method". This entails simply jumping pin 3 of the fog light relay in the engine bay's fuse box to an alternate 12V switched source, such as the tail fuse in the engine bay's fuse box. A wire change at the DRL relay assembly is also required for vehicles with DRLs.
For this modification you'll need:
Rosin core solder (for factory finish
Soldering iron (for factory finish method)
Electrical tape (for factory finish method)
Flat head screw driver (for factory finish method)
Small metric sockets and socket wrench (for factory finish method)
1 .187 size female spade connector (for
quick and dirty method)
1 .250 size female spade connector (for quick and dirty method)
4" of 14 gauge wire (for quick and dirty method)
Mini fuse tap (for quick and dirty method)
The fog light relay grounds through the DRL relay assembly. You need to move this ground wire to another location as part of this modification in order to have control over when the fog lights activate. Disconnect the negative battery terminal. Disconnect the wire harness from the DRL relay assembly. Cut the green with black stripe wire at pin 16 of the DRL relay assembly and either extend and ground it to another location, or do like I did and splice it into the white with black stripe wire, which is a direct DRL ground, for a cleaner implementation. You can see this splice covered with electrical tape in the picture below right next to the white with green stripe wire. If you have the 2002 Toyota Field Service Manual and want to see how this circuit works reference page 88 of the wiring diagram manual. Plug the DRL relay assembly harness back in. You're done inside the truck. The two spade connections in the picture below are for the DRL Switch I wired in.
I wanted to have the ability to switch on the fog lights with the parking lights and have them remain on with the high beams. In a nutshell I wired the fog light relay's power wire to the power wire of the parking light relay. This is the safest thing to do as it prevents you from accidentally leaving your fog lights on and running your battery down as the fog lights will turn off with the parking lights when you kill the ignition. The other option is to run the fog relay's power wire to a constant 12V source allowing you to turn them on by themselves without any other lights, but I don't think this is the best idea since you can run your battery down if you forget to turn them off. I think it looks better to run the fog lights with the parking lights at dusk anyway.
To move the fog light relay's power wire start by removing the three 10mm bolts holding the fuse box in the engine bay to the fender. Remove the lid to the fuse box and carefully remove the retainer on the top left corner holding the large white wire. Be careful removing this wire retainer as it will have a tendency to pop off into the engine bay never to be seen again.
Use a flat head screw driver to carefully disengage the 4 plastic tabs around the edge of the fuse tray that attach it to the box and slide the tray out. You'll be able to see all the wires running to the under side of the fuse tray. The two wires we're interested in are the green with white stripe wire running to the fog light relay (pin 1 12V source) and the black wire going to the tail relay (pin 3 12V source) which is the parking light relay. Cut the green with white stripe wire about an inch from the fuse side. Tape off the fuse side. Strip the relay side about 3/8". Take a sharp knife and slit the black wire going to the tail relay. Solder the green with white stripe wire to the slit in the tail relay black wire.
Tape the connection up with electrical tape and reassemble the fuse box. Now the fog lights can be switched on with the parking lights and will remain on when the high beams are activated. The fog light switch will turn them off or on as long as the parking lights are on, and when you kill the ignition the fog lights go out automatically like the rest of the lights do. As an added benefit, the fog lights will flash with the parking lights when the security system is activated or deactivated as well.
For the "quick and dirty method" simply open the fuse box in the engine bay, pull out the fog light relay and bend pin 1 (12V source) out at a 90 degree angle so that it does not plug into the socket. Plug the fog relay back into the fog relay socket. Connect a 4" piece of 14 gauge wire to this bent pin 1 using a .187 female spade connector and attach the other end of the wire to a mini fuse tap inserted into the tail fuse using a .250 female spade connector. Perform the same ground wire change at the DRL relay assembly. That's it. I chose the more involved method as I did not want to see the jump wire in the fuse box.