[daless2]

DIY: How-To Enable “Anytime” Fog Lights

2007 – 08 Tundra

For $15 or Less

Design by Daless2

Note: I have made updates to these instructions to give you a choice as to how your Fog Lights will perform, based on Ignition Key Position.

Your Options Are:

Option “A” = Fog Light Operate Independent of Ignition Switch Position
Option “B” = Fog Lights “Off” when Ignition Switch is Turned “Off”
Option “C”= Fog Lights “Auto Off” 2-Hours after Ignition Switch is turned “Off”

You get to pick the option of your choice.

I have also added a Version Number to the file name FogLightsVx.pdf where x = a number. The higher the number is, the more current the document.




Overview of Factory Fog Lights


The Factory Fog Light Switch, mounted on the stalk, does not turn the Fog Lights “On”.

Instead, when you turn this switch “On” it makes a “Request”, (via a ground signal) to the Main Body ECU to turn the Fog Lights “On”.

The Main Body ECU then decides, based on a set of rules, if it will supply a ground to the Fog Light Relay “coil”, or if it will supply +12 volts to the other side of the Fog Light Relay “coil”.

The Main Body ECU must supply both a “ground” and a “voltage” at the same time, for the fog lights to turn “On”.

The “rules” which the MB-ECU applies when you “request” the Fog Lights be turned “On” are as follows:

q Fog Lights cannot be turned on by themselves

q Headlights Lights must be “On” for Fog Lights to turn “On”.

q High Beam Headlights “On” cause Fog Lights to “Turn Off”

Basic Design Description


More then a few Tundra owners have expressed an interest in being able to turn the Fog Lights “ON” anytime they want, regardless of the rules that apply to the truck as it comes from the factory.

This design will do this for you by divorcing the Factory Fog Lights both physical and electrical from the control of the Main Body ECU.

This is accomplished by physically removing the Factory Fog Light Relay, installing and wiring up a New Bosch Type Automotive Relay and cutting one wire.

Please Note: You must be willing to cut this wire. DO NOT under any circumstances think you can just “tap” into this wire. If you do you will put your Main Body ECU at unknown risk..

If you want this function bad enough, step up to the plate, suck it in, be brave, and snip it!

As a second feature, this design will allow you to put your Fog Lights back to the way it works now (factory) in about 5 minutes using no tools. This includes the cut wire.

I performed this modification on one 2007 Tundra’s and one 2008 Tundra this weekend.

It works.

If you are reading this as a part of a forum thread, please double click on the “FogLightsVx.pdf” file located at the bottom of this post to view and download the “How-To” instructions.

Note2: Eddie has designed an alternative means of turning on the Tundra Fog Lights.
Being I have the pictures of the connectors involved and their locations I have elected to document Eddie’s design.

Eddie’s single wire solution will enable your Fog Lights to be “On” any time the Tundra Main Light Switch is “On” in any position.

I test installed Eddie’s solution on my Tundra (2007) and can verify it works as designed.

If you are reading this as a part of a forum thread, please double click on the “FogLightsEddieVx.pdf” file located below.




I hope some find this useful.

Have a great night.

Frank