Disable Auto headlights 99-02


Feel some type of way
Mar 8, 2012
Central Jersey
This is the how to I followed for disabling the auto headlight feature on my truck, I added pictures which helps you visual learners:


Basically you will need a pair of wire cutters and a 1.5K ohm 1/2 watt resistor that you can get at Radio Shack. Electrical tape and possibly some wire nuts will work to wire in the resistor. You can solder the wires if you wish.

You may want to remove the neg. battery cable to assure you don't do any unwanted damage to the electrical system. This is not necessary, but a good precaution to take.

First locate the Body Control Module (BCM) which is under the dash, below the steering column. Laying on the floor, this should be visible without removing any dash panels. You should find a purple connector (C3). Unplug it. This is a pic of the BCM and the purple C3 plug that you need to remove and will be working with

Locate the white and gray wires (A4 and A6). I don't remember if white is A4 and gray is A6 or vice versa. It doesn't matter anyway.

Clip these two wires that are coming off this plug (C3). Leave a few inches to work with. Tape up or place wire nuts over the other end of these wires that go up under the dash(they go to the light sensor). You have now removed the light sensor from the electrical system and is now just a dash ornament.

Connect the gray wire from the plug (C3) to one end of the resistor and the white wire to the other end. Make sure you tape up all wires to prevent a short. You should now have a gray wire coming from C3, going to one lead of the resistor and the white wire from C3 to the other resistor lead. Plug in C3 to the BCM and replace the neg. battery cable if you removed it. Start the truck and make sure the lights are off.

I used the wire nuts just to protect the sensor ends they do not establish any sort of connection, I just use them as a cover for the nonfunctional ambient light sensor wires. What you can't see in this pic is I taped up the resistor to isolate the power going through the resistor to prevent power jumping to any other wires and causing a short. Word of advice; if I was to do it again, don't cut the wires at the terminal like I did leave enough wire length to solder on the resistor and have it away from the rest of the terminals. Also note, this mod will not work with just a jumper like 03-07c trucks. The resistor is needed for the auto headlights to be disabled. Mod is so quick and easy don't know why I waited so long to do this. Costs all of $1.50 for a 5 pack of resistors. So now I have 4 extras! Happy New Year and Happy Modding!
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on my 99 when I did this I also added a switch inline so I could turn auto headlights back on, if I wanted it to function as factory/stock.
That is a cool idea I saw it done on some duramax forums. I'm gonna be keeping my truck for as long as I can so I know I will never want automatic headlights.

But that mod would be great for a leased truck!

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Bringing up an old thread but what's the auto climate stuff?

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