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2022 GR86 6AT Base Steel
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Discussion Starter · #1 · (Edited)
The base GR86 doesn’t come with courtesy/step lights. After many hours of research and wire testing, I found the only thing needed other than buying the lights is the ground control wiring from the body control module/body integrated unit (computer) to the door harnesses. The wiring in the door is there and positive lines are live. Please note this process involves repining harnesses, removing pins, splicing, running wire under dash, removing 4 panels etc. I would only do this if you are experienced with car wiring and harnesses.

Do everything with BATTERY DISCONNECTED!!!

Wiring diagram (leads to module are negative side of circuit, other side goes to positive/hot feed from fuse in engine bay via instrument panel harness. We are only working on ground wiring for the whole process):
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Harness locations:

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Remove end cap of dash from bottom slot, it has a lip that faces toward front of car
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Remove 1 screw, then pull lower dash off held on by several friction pins. Disconnect 2 harnesses.
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Remove kick panels on each side, driver and passenger. Pop up the door sill to release it from the kick panel. There is one external pin toward the back and two internal clip pins that get released by tugging on it.

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Run single 18 gauge wire that is within a corrugated wire wrap/conduit from passenger side kick panel to driver side body control unit. I feed it behind blower mounts on firewall then toward center console where plastic triangle and fabric meet.
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On driver footwell where it comes out of, I feed it up over the steering column, way up above the metal frame where some other wires are.
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End of part one.
 

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Discussion Starter · #2 · (Edited)
Wire run in conduit from passenger side goes up over steering etc and around behind computer and sensor modules to the body control module.
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Run additional shorter 18 gauge wire with corrugated wire wrap conduit from driver side kick panel area to body control module.

Obtain some pins to wire in both runs into body contol module. I bought an old Scion FRS unit for $20 and removed a couple. It had the exact same harness and pin size. You split the harness into horizontal pieces and depin by removing the end caps and depressing the clips. It is sort of complex. If you can get some correct size pins it would make your life much easier!

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Take the released pins with wire ends and splice them into your two runs. I used removable crimp connectors on both the cpu and door sides in case something needs removed in the future. I used wired pins with leads that had colors to match the true wiring diagram, white for driver and pink for passenger side.

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These go to middle harness in pin slots 5 and 6 to the bottom left near pin 4 which is red.
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Remove harness:

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Luckily pins 5 and 6 are in the first row so only the top layer of harness needs temp detached to insert our new pin leads.

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Pins go in with pointy end toward harness release, or to the left.

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I labeled the leads even though colors at end match diagram.
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Discussion Starter · #3 · (Edited)
Now we have to terminate the door wire on each side to the 18 gauge leads that go to the body contol unit. It is a small purple wire in right door harness, pin 22 on df19/df20. This needs done on both sides, but I only only showing one.

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I removed the pin by depinning it from the harness then cut it off so I could save length. You could always just cut off the purple wire close the the harness without depinning. To depin, pop up this bar using the two tabs, then using depin tool or similar depin and cut off the pin. Reattach harness.

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Crimp the purple lead from each door to the 18 gauge wire in conduit using removable connectors in case door ever has to be removed etc. Here is the driver side.
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Do the same to passenger side.
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Discussion Starter · #4 · (Edited)
Prepare the lights. The lights are part number 94256AL000.

If you use LED bulbs, be sure to use ones with chips and or solder that doesn’t go to the edge since the bulb holder is all metal (conductive). The Autoix bulbs come in two types in the box. Use the ones with the one chip.
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pop off cover panel under door with pry tool and pry from door hing side of panel!
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Remove panel from harness.
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Attach light and attach your car battery and you should have working courtesy lights now.

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Excellent tutorial! This is what makes a great forum.
 
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Discussion Starter · #8 · (Edited)
@Mugen_89

No, these are ground/negative wires. The body control module controls transfer to ground, driven by door switch input sent into the body control module. It is basically fancy relay switch logic using chips on the board.

The positive lead in the door is hot. The door wiring harnesses are same between base and premium, but instrument panel harnesses are different.

I updated description for wiring diagram as I don’t show the whole diagram.
 

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No, these are ground/negative wires. The body control module controls transfer to ground, driven by door switch input sent into the body control module. It is basically fancy relay switch logic using chips on the board.

The positive lead in the door is hot. The door wiring harnesses are same between base and premium, but instrument panel harnesses are different.

Right, I looked at the frs and GT86/BRZ diagrams and it shows a switch to ground coming from the control unit but in the b-pillar 🤔. So it's the ground like you mentioned coming from the door latch and going to the control unit . So it's def gonna be a weekend project 🤣
 

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Discussion Starter · #11 ·
Right, I looked at the frs and GT86/BRZ diagrams and it shows a switch to ground coming from the control unit but in the b-pillar 🤔. So it's the ground like you mentioned coming from the door latch and going to the control unit . So it's def gonna be a weekend project 🤣
Luckily you don’t have to mess with the door switches that are part of the lock actuators. You only have to wire in the negative side of the lights to the body control module. The hardest/trickiest part is wiring into the body control module as you need to pin in the harness. I got a used unit with the same harness to make sure the female pins I put in mate perfectly with body control unit. The junk control module was more than the lights, but trying to get new female pins that match precisely would be hard then micro crimping them would be harder.
 

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Discussion Starter · #12 ·
Update: I had the whole dash apart to install a line out converter at the head unit, so I rerouted the passenger side ground through the channel above the glove box instead of footwell area. I am glad I used quick disconnects. Here is a photo of the area before I ran it and the red is the new path from driver to passenger side. I used the following video to remove things, you will get what I am talking about.

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Discussion Starter · #16 ·
The dome, trunk, and courtesy lights are all the same, 194 wedge bulbs. Be careful with LEDs in the courtesy light holders as they are all metal. See my install notes above.
 
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