I think I'm gonna just give up on this.
I dove into my FSM as well.
According to it like you mentioned the light is supplied directly without the ECU's involvement.
It's supplied 12V - of course and then it has a ground switches:
According to FSM here are the wire colors
1. Brake fluid switch - R/B
2. Parking Brake switch - V
3. Ignition switch - V/R
All three seem to simply complete the ground.
Cool - I think. I already verified the brake fluid and parking brake so I'll check the ignition for a problem.
Well... the problem is that the Brake fluid is R/B. Cool.
But my Park brake is V/W. Not V. I go: WTF?
I figured that's the problem I connected a wrong wire somewhere. Well. No. I have no Violet wire anywhere on top of the trans tunnel harness.
Also. I have no V/R coming out of the ignition switch. Nothing even close. I got really confused. It almost seems to me the FSM is wrong but I've never seen this before.
I'll just learn to live with the light. Maybe just loose the bulb so it's gone and keep checking my fluid or reg basis...
IDUNNA.