I'm in a problem with this one as well
I thought it's working wrong but now I think it's fine and it looks like the MR one do work else as the Celica one. If you detach the plug from the sensor, you can see that the ECU gives 5V to it and the sensor reduces this value as heat grovs.
One thing I don't understand:
The RedTop wiring diagram that can be found on the net shows this sensor having 2 pins only, while it do has 3! What's the third one for? And why this diagram doesn't show it?
midnite, I searched the EPC and it gives 3 different part numbers for this sensor, all for MR and all made from 97.12., so I don't know which one is the needed one :S