Installing JDM rear fog light as a brake light

DeusExMaxima · 01-31-2022, 02:37 AM

The picture shows the rear sub harness and the drivers side brake/tail light harness. It's a bit cramped for space, but it's better than adding a whole new harness to the car!

Lannyl81 · 02-05-2022, 10:41 AM

Going from my memory (not always correct anymore), the power wire at the rear fog lamp is orange, return(ground) is green....or maybe black....do not recall 100%.
The orange wire runs to the BCM which powers the factory fog lamp.
Hopefully this is the wire you cut to splice into the rear brake light harness. Do not want to have +12V connected to the BCM output.

Bottom line is that you got it to work the way you want it.....good job!!

cooltoy · 02-05-2022, 12:02 PM

Quote:

Originally Posted by DeusExMaxima

Ok...I figured it out. This procedure is to hook up the JDM foglight as a brake light. It can be used to hook up the light as a running light too or whatever you wish. The key is that no external harness is necessary. It's already in the car.

The process is as follows:

1. Pull the trunk paneling away
2. Locate the wires going to the brake light assembly.
3. Pull back the electrical tape and expose the wires of both the subharness going to the rear and the wires running to the brake/tail light.
4. Dig in the harness and pull up the yellowish wire.
5. Cut the wire. This is the key since it runs to the BCM.
6. Join the yellowish wire to the green wire coming from the brake light. Either solder or butt connector.
7. Plug in your fog light to the oem connector.

You now have a 4th brake light without using an outside harness. The ground wire is already grounded. You don't even have to remove the tail light.

I would recommend doing up a DIY post in DIY section, otherwise this will eventually get lost in the pile of the rest of new threads. Or ask the mods to move this there. At least there it would be easier to find.

DeusExMaxima · 02-05-2022, 03:26 PM

Quote:

Originally Posted by Lannyl81

Going from my memory (not always correct anymore), the power wire at the rear fog lamp is orange, return(ground) is green....or maybe black....do not recall 100%.
The orange wire runs to the BCM which powers the factory fog lamp.
Hopefully this is the wire you cut to splice into the rear brake light harness. Do not want to have +12V connected to the BCM output.

Bottom line is that you got it to work the way you want it.....good job!!

Thanks. Yes it is an orange wire that goes from the foglight to the BCM. By snipping it at the junction of the tail light loom, it takes that wire out of the BCM circuit and you can easily hook it up to the brake or tail light which are right next to it. That's the beauty of this mod.

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02-05-2022, 10:41 AM	#17 (permalink)
Lannyl81 Base Member Join Date: Jun 2021 Location: Tucson Posts: 58 Drives: 2018 370Z Sport M6 Rep Power: 4	Going from my memory (not always correct anymore), the power wire at the rear fog lamp is orange, return(ground) is green....or maybe black....do not recall 100%. The orange wire runs to the BCM which powers the factory fog lamp. Hopefully this is the wire you cut to splice into the rear brake light harness. Do not want to have +12V connected to the BCM output. Bottom line is that you got it to work the way you want it.....good job!!