exhaust temp warning light wiring question

[toyotahachiroku]

the car is a 11/90 JZA70

the exhaust temp probe has been removed and the wiring to the probe has been individually capped off. the exhaust temp warning light will light up occasionally. sometimes it will stay on through out the drive. but, pressing the brake pedal makes it go away. release the brake pedal and it comes back.

i have a few questions.

what does the stop/brake signal from connector T pin 14 provide to the ecu? what happens if it doesnt see that signal?

does the probe increase or decrease in resistance when the exhaust heats up? under what conditions and how does the probe light up the warning temp? is it case grounded at all?

would there be any know common issues with the wiring on these cars where the exhaust temp wiring between the bulb and pin 7 of connector U be grounded on the brake/stop light wiring between pin 14 of connector T or with the stop light switch and or stop light ground?

this problem has been bugging me ever since i got the car. any help would be appreciated!

 

[annoyingrob]

I believe the probe decreases resistance when it heats up. If the light is coming on, I would believe that the wires are shorting out somewhere. If it goes off because the brake lights are on, It's probably a grounding issue in the wiring.

You say the wires for the probe are capped off, are they capped off in the floor of the car, or capped off at the ECU? If the wiring is still in the car, cut it off at the ECU.

 

[Krister]

I have a downpipe without a cat and the temp probe is under the car. Should I unplug it for some reason? Any benefits in doing this?

 

[annoyingrob]

I have a downpipe without a cat and the temp probe is under the car. Should I unplug it for some reason? Any benefits in doing this?

It doesn't matter. All it does is turn on a light.