1. Welcome to The Truck Stop! We see you haven't REGISTERED yet.

    Your truck knowledge is missing!
    • Registration is FREE , all we need is your birthday and email. (We don't share ANY data with ANYONE)
    • We have tons of knowledge here for your diesel truck!
    • Post your own topics and reply to existing threads to help others out!
    • NO ADS! The site is fully functional and ad free!

    Problems registering? Click here to contact us!

    Already registered, but need a PASSWORD RESET? CLICK HERE TO RESET YOUR PASSWORD!

'01-'02 Duramax All On Headlight Mod

Discussion in 'Do It Yourself Articles - How To's & Product Revie' started by RYDNHI4X4, May 3, 2008.

  1. RYDNHI4X4

    RYDNHI4X4 Halt Halt Or I'll Release My Dog

    May 3, 2008
    San Antonio, TX
    There have been a million posts on headlight mods, most have been with the fuse box. I wanted a better controlled approach that I could change the configuration on the fly. After much searching for the various pieces of information I have finally configured and installed the following circuits on my 2003 Canadian 2500HD.

    First of all this is not the simplest approach. There are actually 5 different circuit modifications being performed here and I will go through the details of each of these. This mod does require decent soldering skills and patience when dealing with the wiring. It's not difficult.

    First have you ever wanted to have those auto headlights work the way you really thought they should work. When you start up the truck and are parked, the auto night sensing headlight should not come on. When you put the truck in gear and if it senses that it is dark enough the head light will come on automatically. There is no need of delay timers. For my 03 All that is needed is standard automotive headlight relay cube, diode, wire and connectors. This is the top part of the circuit.

    If this is all you want then all you need to do the following. Run a wire from the green brake line wire to the relay. This wire provides 12V only when you are in Park so the relay will only be energized while parked. (Our starting condition.) This supplies power to the coil of the relay. The other side of the relay coil just needs to connect to ground. Hence the relay will only be energized when in Park. Since these standard cube type relays use push on spades, crimp connectors are all you need. That is relay power. The relay numbers on schematic have no meaning as you will have to find what is relevant to the relay you get. Look at schematic of relay to find pin number correlation.

    Now relay contact to disable headlights. All you need to do is run wire to BCM C3-pin A4 to the wiper contact. Drawings on relays are always shown in de-energized state so we want to make a circuit when relay is energized. So on the normally open contact you can attach a diode using crimp spade lug. The white line on the diode corresponds to the line in the diode picture. The diode lead without the white line is what gets connected to the relay. Then using spade lugs or but connector attach wire to white line side of diode. Take and attach this wire to BCM C4 pin B7. You can find the numbers listed on the shell of the connectors. For connections to the BCM wires I like to use those red slice in tap on crimps that you don't have to cut any wires and just need a pair of pliers to push the blade down into the wires for contact. Red ones are good for wires up to 18guage. The BCM wires are a 20ga I think.

    Viola, you now have auto headlights the way it should have been. (Oh I guess I should be careful this probably is not possible for those with manual transmissions) There is a slight delay (approx 30 seconds) before the BCM will turn on the headlights. The delay is to compensate for quick light fluctuations. Also when you arrive at destination and park your headlights automatically turn off after the prescribed delay time.

    The next circuit was my adaptation of the High idle circuit. Since it uses the green wire for power, I ran it through a switch so I could positively disable the high idle in conditions when not needed at all. I use the LED indicator to indicate when the Switch is on and also when power is applied to enable the high idle circuit in the ECM. Again pin 71 as well documented on other posts and Kennedy diesel site. Be aware there is an error I think on the pin contact part number 12084913 is for 20-24ga wire and 12084912 is for 18guage wire. They are sold as individual pins. Get appropriate one for the size of wire you run.

    Next switch down is to disable or cut out the Low beam head lights. Even with the auto headlights there has come the time where I need to switch off the headlights. Driving into a star gazers party or a campground late at night. Need to switch of main headlights. By the way if you have fogs this will allow you to run with just your fogs on for those type of conditions.

    To do this you will actually have to cut the pink wire going to the BCM. I installed bullet connectors or spade connectors, one male and other female so that if desired can return to stock condition without any soldering. Just reconnect male to female connectors. Normally this circuit is closed so the switch is wired that when switch is up it breaks the current path pink to pink going to the BCM.

    The next switch is a tap off that will allow the use of a diode to allow the low beams to turn on when the high beams of on. Again the diode direction is what allows this to happen. When the switch is up it makes a diode connection between low and high beam circuits. You now get high and lows together when high beam is selected. If you reversed the diode you would get high and low beams together when lows were selected (Not a good thing).

    The final switch allows the same ability to select fog lights on when high beams are selected. Same exact principles exist as the previous switch. So now you can tailor exactly what lights you want on when you select the high beams according to the driving conditions you are in. I would recommend not more than 2 additional circuits onto the high beams. If you wanted DRL instead of fogs the lower right indicates the substitute CBM connection for the DRLs you would use.

    Again this is much more complex but you now have the ability to configure your headlights exactly to the driving condition you encounter.
    Last edited: Sep 22, 2009

Share This Page