How To Wire Accessories To Factory Aux Buttons & Harness

[k2idle]

When I first went to wire my lights into the factory AUX buttons I was really confused to say the least. I was not well experienced with vehicle wiring and I thought it would be simple plug and play, but there are capped connectors, different amp ratings, and a lot of mixed info out there. I ended up watching a bunch of videos before it finally made sense, so I wanted to put all the info in one place.

The basics:​

• The Tacoma comes with three AUX switches from the factory on certain trims
• AUX1 is 15 amps, AUX2 is 10 amps, AUX3 is 5 amps
• Each AUX switch already has its own relay and fuse in the factory fuse box
• The connectors are capped and tucked on the driver side of the engine bay near the fuse box
• There are three plugin locations around the truck 1 in the engine bay 1 underneath near the front and 1 in the rear

The harnesses:​

• Toyota includes 2 harnesses i've heard some people getting 3 but I only got 2
• The main harness has 4 colored wires on one end and a plug in adapter on the other
• The second harness is identical to the first but only has 3 wires if you want to send power to the rear
• Main harness wire colors on the AUX harness usually line up like this:
  • Black = AUX1 (15A, good for bigger stuff like a front light bar)
  • Green = AUX2 (10A, good for medium loads like ditch lights or compressor trigger)
  • White = AUX3 (5A, best for accent lighting or low-powered accessories)
  • White/Black Striped = Ground
• Second harness wire colors on the AUX harness usually line up like this:
  • Black = AUX1
  • Green = AUX2
  • White/Black Striped = Ground

Wiring steps:​

• Splice your accessory to the desired wire
• Locate the capped connectors
• Remove the weatherproof cap
• Insert factory wiring harness
• Enjoy your easy installation

Things I wish I knew:​

• The AUX switches are ignition-switched from the factory; they don’t work with the truck off unless you rewire the relay box
• Each AUX circuit already has its own fuse and relay; you don’t need to add more unless you’re running higher draw gear
• There are aftermarket adapter harnesses that plug right into the Toyota pigtails if you don’t want to splice anything
• Make sure you look up your accessories draw beforehand

Accessory ideas:​

• AUX1 (15A) is perfect for a front light bar or multiple pods, especially through a relay
• AUX2 (10A) works great for ditch lights or a compressor trigger
• AUX3 (5A) is a good fit for accent lighting, grille lights, or to act as a relay trigger for rear scene lights
• The bed 12V outlet is fine for bed LEDs, a small work light, or charging smaller electronics, but not for anything high draw

This way everything works like factory and I didn’t have to add an aftermarket switch panel. Hopefully, this helps someone else avoid the same confusion I had when I first tried to figure it all out.

 

[rustytaco]

Good info. I only used one harness and plan on keeping all those leads near the engine bay. Not too sure either about the extra wiring locations or harnesses. I thought you could only send one lead to a secondary location, and didn't know about the one in the footwell. Keep us posted on what you learn!