This guide will help anyone looking to hook up auxiliary lighting (any triggered by a relay) or to disable DRL's on Base/Premium 18+ WITHOUT factory LED headlights only.
This guide is provided as-is for informational purposes, any repercussions (legal, physical, and or thermal) are your own responsibility.
For this guide you will need two 5 pin Relays (the guide will assume your lighting is triggered by a relay as well) and two pigtails for them, you should be able to find them at any local auto/electric supply store.
2-12v 5pin relays
2- 5 pin relay pigtails
Misc wire (I used 16g red and black)
(Only 1 relay/pigtail will be used if you are not equipped with fog lights)
We will be using the following diagram to reference for all wiring points, note that depending on if your relay is normally closed or normally open your #87 and 87a may be reversed.
The two relays will be referred to as R1 and R2.
R1 is going to be the low beam sense relay. R2 will be the fog lamp sense relay.
First I will outline the lighting guide to use Hi-beam voltage as a trigger for auxiliary lighting, the next part will be to disable DRL.
I would recommend tapping all 3 of your outputs needed for either lighting or DRL disable before continuing
I accessed the low beam and high beam on the passenger side headlight plug as it was easier to fit the soldering iron once the intake snorkel and the trim beneath it are removed. Either side headlight uses the same color wiring points so it’s just preference or for me personally just ease of access.
There are two wires at this area you need to shave back the coating and solder a wire onto:
Red: Low beam output
Orange: High beam output
The wire you use does not have to be a huge gauge as the load of the lighting is not passed through these wires we are tapping at the headlight, and we are just using them to signal a relay so the draw will be negligible.
Now for the fog lamp I chose to do the driver side, just because it was closer to my mounting point for the relays.
Remove the front clips and 2 side clips on the lower fender liner front section on the bottom. You will not be completely removing the liner but just folding it back. It may help to lift the vehicle with a jack.
Once that cover is peeled off there is one philips head screw to remove and you can bend the panel back slightly and gain access to the fog lamp.
Here you will tap one wire:
Purple: Fog lamp output
Now that we have our 3 outputs on wires I will refer to them for wiring as:
Low beam: LB
Hi Beam: HB
Fog lamp: FL
Now all relays need to be grounded on pin 85 or 86 (depending on your pigtail the color may be black or different). I chose to ground on 85 since it was black for my pigtails for ease of color similarity.
I recommend doing this all as a dry run first, just strip the wires and twist them together to verify function. Then follow up with solder/heat shrink afterward.
*If you do not have fog lights on your vehicle then proceed to wire the one relay from the low beam relay (R1) and wire directly into your lighting relay.*
For aux lighting follow the below steps:
1.R1 wire the following (assuming 85 as ground & 87a normally closed)
LB to 86
HB to 30
87 to R2 pin 30
CUT or tape off 87a
2. R2 Wire the following (assuming 85 as ground & 87a normally closed)
Pin 30 should have the output from R1/87
FL to 86
87A to Aux lighting Trigger wire for relay (usually 85 or 86)
CUT or tape off 87
3. Mount all relays and zip tie, and hide all wiring as much as you care to do.
You have completed your aux. lighting trigger, this wire will now only see 12v when the low beams are on and it will ensure the fog lamps can also be turned off as well without the light bar coming on. Auto headlamps and DRL’s will still function using the above wiring as well.
Now for the DRL disabling. I don't recommend doing this, as you will have to CUT both the orange high beam wires and suffer your own warranty voiding etc, if something should happen all liability is on your own choice to disable them.
Note: If you do not have fog lights then you will be using only one relay to check if the low beams are on and wiring the same procedure below.
For this you will not have a 3rd relay to wire to trigger, you will be wiring back into the orange plug at the head lights. You also can only use one relay if all you care about is disabling DRL, and if your state/police don't care if your fogs are on with high beams.
1. Cut the orange hi-beam wires at both head light plugs, leave enough on either side to connect wires.
2. For this guide we will refer to the car side of the orange Hi beam wire as CHL and the plug side of the head light orange wire as HHL
3. Wire the following (assuming both relays are grounded at 85)
CHL to pin 30
LB to 86
87 to R2 pin 30
CUT or tape 87a
Pin 30 is output from R1 pin 87
FL to 86
87a to HHL
CUT or tape 87
This will ensure your high beams only come on with the auto headlamps or when manually turned on. Fog lamps etc all work the same, but no voltage will make it unless the low beams are active (thus no DRL).
Also note this procedure will work on *any* Subaru using PWM to dim the high beams as daytime running lights. However the colors of the wiring may be different, you will need to use a test light or multimeter to ensure you are tapping the correct wires at the headlight plug and fog light (if equipped). Other than the wire colors being different it is electrically the same wiring procedure to remove the DRL signal to the hi-beams and only have it come on when the headlight system is activated with the low beam trigger.
After researching LED Hi-beam bulbs online, I noticed the above DRL delete procedure would also make any aftermarket LED bulbs work with the low voltage system Subaru uses. Many suppliers (PIAA,Putco) claim their bulbs support PWM signals for the CEL or check light status signal (but not the actual power supply to the bulb). So using the DRL delete method you ensure that only 12v gets sent when the high-beams are on.
Hopefully this guide will help someone, it took some head scratching and staring at relay diagrams but was well worth it to get the LED bar onto the Trek without having to run a wire into the cabin.