This is a cool Mod I did this weekend. Thanks to angel2167882 on B15 for his write up. I have added some of my own pics…
History
Well since 1989, every vehicles sold in Canada should be equipped with daytime running lights for security purpose. This mean that at least a pair of front lights should ALWAYS BE ON (intensity may vary from full light). You can find more info on that law here: http://www.tc.gc.ca/en/faq/road.htm#daytime running lights.
Why to do it?!
Well, U.S. model don’t have it, so why mine should? Also, with the headlights always on, they will burn out earlier and I want to take care of my PIAA ;). And finally, the look is so cool without it. Plus, I really don’t think any cops will bother me with that. If so, the surgery is reversible easily!
The Basics
So, how it works? Simple. Every Canadian B15 (and probably every Nissan) headlight wiring pass by a module call the Danytime Light Control Unit (DLCU). This module controls every aspect of the headlight including daytime light, low beam, high beam, car park, etc). The daytime light only work when every others lights are off. Once you turn on parking light, low or high, they will “turn off”. The daytime light are actually the high beam headlight wired in series, thus operating at half illumination.
This idea came to me because when the parking brake is apply (pull) before to start the car, the daytime light WON’T turn on. So, the easiest way to disable the daytime light are to fake the DLCU by let him think the parking brake is always apply. That way, headlight will work as usual without the daytime light when everything else is off. Also, after the mod, your “brake” cluster warning light will still be fully functional and operate as normal.
Part needed:- Only 1’ of 16~18 gauge size wire (can be done even without it)
Tools needed:- Screwdriver set- Wire skinner/cutter- Electrical tape
Time required: 30 minutes
Skill: Easy
How-to step-by-step:- Remove key from ignition (if so)
- Open the driver’s door
- Apply (pull) parking hand brake
- Locate and remove the plastic screw-nut on the lower left dash garnish panel
- Pull the lower side garnish a bit to free up the other one
- Remove the plastic garnish
- You now have access to the DLCU (the black plastic box)
- Unscrew the metal harness
- Locate the light green wire. This wire goes (not directly) to the parking brake switch. When brake is apply, ground (0V) is on that wire; when parking brake release, battery voltage (+12V) is on that wire.
- Cut and skin it
- Isolate with electrical tape the wire coming from the hand brake switch
- Tie and tape the 1’ spare wire to the connector side wire
- Skin long enough the spare wire and wind around the harness screw. This will fake the DLCU by always sending a ground signal and thinking the parking brake is applied.
- Plug back the connector
- Screw back the harness with carefully being sure wire is under the bolt
- Test your setup
- Put back the plastic garnish
- You’re done!
Optional
A switch to the mod is great. At least now, the mod is totally reversible with simply a touch of a button 
(good for aware cops)
As for the switch itself, let me just tell you that you need a “ON-ON”, 3 pin switch. This is because if the light green wire is not grounded anymore, it need to make a contact with the original cable. If you use a regular 2 pin switch, the signal going into the DCLU will be “floating” and this is no good in electricity. Let me explain it in details…
Wiring with switch specs:- Switch to OFF: Contact is made with the ground screw and the light green wire going into the DCLU (like the original mod)- Switch to ON: Contact is made with the light green wire end-to-end (like the factory setup)
Hope you understand… if not, don’t worry, I have enclose pics just below 
Switch and hole cut into the garnish:
Switch wiring with the actual mod:
Oh and last thing… once you turn on the switch while the car is running, the day light WON’T come off if the switch is turn back off after (until engine is turn off again). This is exactly like how it work with the hand brake on the stock setup.
Now I think my mod is complete 