DRL Disable with Auto Headlights

Midnyteryder196

Well-Known Member
#1
DRL Disable with Auto Headlights

This write up will be to disable the DRL function. This method uses a relay spliced in at the bcm and will disable the DRL, along with keeping the auto headlight function, but It will also disable the low beam's night time perimeter lighting function while remote lock/unlocking. Disabling the DRL is beneficial when installing HID low beams as the pwm signal of the DRL decreases the life of the ballasts.


Summary: Disabling DRL while retaining Auto Headlight Function
Difficulty: Easy to Moderate
Estimated Time: 30-45 min
Total Cost: $10-$20

Required tools:
Wire stripper/cutter
Crimper
2x red butt connectors
2x red scotch lock connectors
1x 4 pin relay, preferably with relay socket to make installation cleaner
4x Random lengths of wire with a female spade connector on one end of each wire if not using a relay socket

Note: Being we are going to be working on the bcm connectors, if you are not comfortable with electrical wiring then find someone who is comfortable doing it. The author takes no responsibility if you mess up the wiring, or worse yet the bcm. Also as like any electrical modifications, DISCONNECT battery before preforming any work on the electrical system.

We will be using this diagram to install the relay into the wires at the BCM.
Also the relay socket I am using has the wires color matched to the BCM.
Trailblazer DRL Disable.jpg


1. First we have to access the BCM. Short wheelbase models will need to pull up on the rear driver side seat to expose the fuse box cover, and then remove the cover off the fuse box and BCM. Long wheelbase models will need to remove the driver side second row seat to gain enough access to the BCM, once the seat is removed you will be able to take the cover off of the fuse box to access the BCM.
2. Once we have access to the BCM its time to disconnect both plugs on the side of the BCM (a gray plug, and a tan plug). From here you will need to remove some of the tape around the wires to give you enough room to cut and tap into the wires we need to.​
3. Find the pink/white wire in pin A5 of the gray plug. Follow the wire back about 3-4 inches and CUT then strip the ends of each of the wires.​
4. Next we will use a butt connectors to connect the pink/white wire from the BCM to pin #30 of the relay, and the pink/white wire that goes into the wire harness to pin #87 of the relay.​
DRL Install 1.jpg

5. Next we will find the white wire in Pin B6 of the gray plug. Follow the wire back about 3-4 inches away from the plug and use the scotch lock to connect the wire to pin #86 of the relay

6. Finally, on the tan plug find the pink wire in pin E7. Follow that wire back about 3-4 inches from the plug and use the scotch lock to connect the remaining wire to pin #85 of the relay. When done it should look similar to this.​
DRL Install 2.jpg
Once all connections are made, plug the relay into the socket, connect the battery and make sure the DRL is disabled. Once everything checks out, find a secure place for the relay, install the fuse box cover, and replace the rear seat.


.​
 

l008com

Well-Known Member
#2
So if I read this right, what this does is only allow the low beams to come on when the Headlamp On Indicator Control is powered? What is that exactly?

I was under the impression that my DRL's were low power high beams, which makes this even more confusing. But maybe I'm wrong and on this truck DRL's are low power low beams?

Also if the relay used has the pin for the 'off' switch (87a), would that extra pin work as a custom, full 12v (no PWM) powered DRL that would turn off when the headlights went on?

So say I do an HID retrofit here, I'll need to kill the factory DRLs. But say I want to add my own custom LED DRL's that would be powered with ignition power, but relay-switched off when the low (or high) beams came on.
 

Matt

Silver Supporter
#3
The DRL's are the low beams run at about 70% of power, hence the need to either disable the DRL or do the capacitor mod to run them at 100% if you retrofit HID's.
 

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