Update: I just received a reply from DD about what I should do:

"Thanks for reaching out! In this particular case, I wouldn't tap the low beam, as your foglights (the main beam on the SS3s in this case) only turn on when your headlights are on anyway. Additionally, anywhere in the engine bay should be just fine, as the Crosstrek does a great job of limiting exposure in the engine bay. If you were worried, you could simply apply a little dielectric grease and wrap the connection in electrical tape (though the tape should be enough).

Finally, the DRL wires should be light blue on all trims (apart from the hybrid) and the sidemarker wires should be a traditional blue. I would probably recommend the DRL wires myself, as the parking lights will generally come on with your low beams (when you would probably want to run your foglight main beam)."

I'm not sure my 2019 premium has DRLs but maybe there's parking lights? Will investigate.

 

Just purchased the DD SS3 LED Fog Light Kit and am in the process of installation. Bumbleface what source did you finally connect the backlight wiring to? And are you happy with the choice and operation?

 

I haven't had the weather or the time quite yet to rip everything apart and get familiar with the wiring. I'm also not very familiar with my 2019's exact conditions for each light to be on or off...I don't even know for sure if I actually have DRLs. Maybe its the side marker bulbs, or maybe its the high beams with lower voltage? I've been trying to do internet research but it's not helpful as there are so many trims and model years now. I think I'll actually have some time tomorrow. I'm guessing I'll most likely use the wires DD recommended. I'll get on this as soon as I can and get back to you.

 

Hi, which wire did you end up tapping to? I have the 2019 Premium as well, I want to tap to the DRL but could not find the wiring for it. If you already did it, would you mind taking a picture? Thanks a lot!

 

I forgot to mention, they sent me these diagrams as well.

 

Just replaced the Baja Designs with the DD SS3 Pros (backlit) today, using the side markers with the wire taps.
Works fine, but I wouldn’t mind pulling from the DRLs for the backlights, if anyone has figured out yet where those wires are.
Frankly, I’m just happy to have some fogs in that fit, and don’t require me hacking up the fog light surrounds.
I’m also impressed with the wiring harness quality on the Diode Dynamics units over the Baja Deaigns: proper Deutsch connectors vs no-name janky crap haha!

 

Woo I finally did it! The box only sat for 7 months. Sorry all. The worst part was wrestling with the pop clips under the fog lamps themselves, ugh.

Ok so all I did for wiring the backlights was snip off the connector that they so nicely crimped on the end for us, and used a t tap to connect into the drl wire. The wire is almost exactly as the diagram DD sent me shows. There is a big gray plug with many colorful wires running to it directly below each headlamp assembly, about middle of each. For me, the R/passenger side one had something like 2 black and white wires, an orange, maybe a pink or something, but also a light blue. The L/driver side is similar but has 2 brown and white wires (instead of black and white) along with the other colors. It also has the blue. The blue wire is the drl wire that I t-tapped the fog's backlight wire to on each side. Worked perfectly for me. I just had to (carefully) cut open the tape over the wires off the plug to give myself a little more space to tap.

Also, I used regular t-taps because I didn't really like the ones DD sent with the lamps. I don't think it matters.

It got dark as I finished, but I can try to take photos tomorrow. Here's the diagram DD send me again for reference. I can't speak to what color the wires are on newer treks but I would hope they kept the same scheme.

EDIT: Upon rewatching the video I took to check if I was successful, I am thinking that the backlights came on with the side markers and not just the drls. I may have actually failed. I will investigate further.

 

Woo I finally did it! The box only sat for 7 months. Sorry all. The worst part was wrestling with the pop clips under the fog lamps themselves, ugh.

Ok so all I did for wiring the backlights was snip off the connector that they so nicely crimped on the end for us, and used a t tap to connect into the drl wire. The wire is almost exactly as the diagram DD sent me shows. There is a big gray plug with many colorful wires running to it directly below each headlamp assembly, about middle of each. For me, the R/passenger side one had something like 2 black and white wires, an orange, maybe a pink or something, but also a light blue. The L/driver side is similar but has 2 brown and white wires (instead of black and white) along with the other colors. It also has the blue. The blue wire is the drl wire that I t-tapped the fog's backlight wire to on each side. Worked perfectly for me. I just had to (carefully) cut open the tape over the wires off the plug to give myself a little more space to tap.

Also, I used regular t-taps because I didn't really like the ones DD sent with the lamps. I don't think it matters.

It got dark as I finished, but I can try to take photos tomorrow. Here's the diagram DD send me again for reference. I can't speak to what color the wires are on newer treks but I would hope they kept the same scheme.

EDIT: Upon rewatching the video I took to check if I was successful, I am thinking that the backlights came on with the side markers and not just the drls. I may have actually failed. I will investigate further.

I think the best approach is to tap to the fuse box (just need to find the right fuse so amber light will be on with ignition on), the thing with tapping to DRL harness is if the model doesn't come with LED DRL (like premium models, where high beams are also DRL), then amber light is gonna flicker. Same thing happens when you try to replace high beam halogen bulbs with LED. If the wiring on one side (passenger side) is too short to reach the fuse box you can tap it to the driver wiring then > connect to the fuse box. I've been too lazy to touch them so let me know if you choose that route .

 

Figured I’d chime in.

Recently upgraded from the SS3 Sport yellow w/o backlight to the SS3 Max yellow w/backlight.

Upon contacting DD, Thomas C could not confirm which wire to actually tap into, but after several emails back & forth, he suggested I tap into the headlight side markers.

I cut off the t tap connector & hardwired the backlight wire into the side marker red wire on both sides. The provided t taps are junk. I advise not using them.

Backlight works perfectly after almost a month & the SS3 Max provides an awesome upgrade vs the Sport.

I particularly like the backlight function with the LED headlights in my limited. It gives the front a cool modern type appearance.

 

Figured I’d chime in.

Recently upgraded from the SS3 Sport yellow w/o backlight to the SS3 Max yellow w/backlight.

Upon contacting DD, Thomas C could not confirm which wire to actually tap into, but after several emails back & forth, he suggested I tap into the headlight side markers.

I cut off the t tap connector & hardwired the backlight wire into the side marker red wire on both sides. The provided t taps are junk. I advise not using them.

Backlight works perfectly after almost a month & the SS3 Max provides an awesome upgrade vs the Sport.

I particularly like the backlight function with the LED headlights in my limited. It gives the front a cool modern type appearance.

You have a limited trim! I've since upgraded to a 2023 limited and I'm still not sure what the best choice for the backlight wiring is. You wired into the side marker wires at a point right before they enter the headlight housing?

 

I haven’t had the time to take fresh pics especially with the cold weather, but I attached another pic I forgot I took along with screenshot of email conversation with DD. I definitely don’t recommend using the t taps. During the install I started the vehicle multiple times to test them & they only worked once or twice. That’s why I decided to hardwire them. Let me know if there’s any questions!

 

Here is a pic of my 2019 Limited with backlight on. I did not have the car in drive or the parking brake off so no LED DRL. Mine is set up to be Backlit whenever the car is on and the DRLs when in gear. my power is pulling from the tap in the fusebox.

 

Here is a pic of my 2019 Limited with backlight on. I did not have the car in drive or the parking brake off so no LED DRL. Mine is set up to be Backlit whenever the car is on and the DRLs when in gear. my power is pulling from the tap in the fusebox.
View attachment 325635

Those are the elite fog lights, I like those a lot.
I’m guessing you tapped a fuse, which is an option for some, but requires running more wire into the cabin? Probably a better option for those with a newer model or a lease.
I hardwired into the parking lights so the backlights are on all the time.
I wish more people had chimed in so we’d get multiple wiring ideas