So I went to AutoZone today to pull a code, since my CEL appeared, and turned out I need an O2 sensor replaced ...
However, when I looked under the dash to plug it in, I not only found a light I've never seen before (could be the OEM floorlight, like on the doors), but I also found a random toggle-switch installed, right beside the OBD Plug ...

What the heck is it?

I flipped it, thinking maybe the original owner was shady, and wanted to switch-off the odometer?
So I flipped the switch and drove a mile, but my odometer registered the mile.
So okay, it's not an odometer toggle.

Nothing (that I could immediately tell) really changed, having driven with the switch flipped, so I just put it back to it's original position.

Anyone have any idea what this little switch is for, or could-be for???

 

It clearly looks like the switch to engage the turbo and turn on the NOS. Every SC has that.

 

follow the 2 red wires in photo, they seem to be going to toggle.

 

I have one under my dash as well. Do you have aftermarket remote start or alarm? That is what mine is for.

 

Interesting.
My alarm system is OEM - Red "security" light on gauge bezel, w/ key fob.
I'll have to try though, and see if it disengages it; however why would you need to?

 

I wired in an ignition kill switch once, but it had intermittent problems so I disabled it and left the toggle behind. It could be something like that.

 

Doesn't look oem, we won't know what it is.

Best bet, follow the wires.....

 

Agree on might be ignition kill switch. Or if car had/has a double din radio it can be a bypass for watching did movies.. or maybe electric fans conversion switch?
but yea follow wires

 

you will have to follow the wires, could have been for lots of things an amp/sub in the trunk, alarm.. usually its an ignition kill switch, but I have seen people do it for the speed signal to the ecu for speed cut on jdm ecu's but on US cars its like 150mph I dunno why someone would be going over 150 in a 400 enough to install a switch. I am thinking it was for interrupting the remote amp line to manually be able to turn the amps off. I know I had that in one of my cars that used to help the battery not drain.

 

What do you mean "speed cut"?
Like a governor of sorts?
I've topped the engine out at 147.

 

Is it a PUSH switch or an Toggle two sided toggle switch? when i had my old car (around the SC300 era) there were some OEM alarms that had a push button that when the alarm went off, and say your FOB battery died, you can put the key in the ignition, turn the key (the alarm will sound) and push the button and turn the alarm off. Kind fo like a failsafe. These buttons are usually under the dash.

It could also be for NOS. My buddy recently bought a vette, previous owner swore it was never raced, put on NOS but found the switch and all the supporting hardware for NOS. Those are the only two things i can think of in the older SC's

 

It's a toggle.

I tried to switching it both directions (on/off) and starting the ignition to see if it was a kill switch, but it ran both times. However, what I did notice is that when the switch is on, the car revs differently. It takes it's time revving upward, whereas it revs more quickly when I don't flick the switch. In other words, the gear-change normally at 5000rpm, goes beyond 5000rpm with the switch on. Both the acceleration, and the change from 1st to 2nd are also smoother.

Do these results sound like any "particular" mod, anyones heard of?

Im gonna do a run on the high way, both with it on, and off, and I'll video record it on my iPhone.
Maybe we can solve this without me having to take apart the dash to route wires, and stuff.

 

Is it a SC400? It sounds like the transmission solenoid bypass I just learned about yesterday.

https://www.clublexus.com/forums/per...s-free-13.html

 

It's an SC300 ('97)

 

Hmm, unless that mod also works for the SC300 (someone just asked that question tonight), then that's a dead end.