This is information that I can get from the Toyota technical guys. I don't believe this info is available in any factory service manuals. This info is available buy using the Vetronix MasterTech diagnostic scan tool to either the diagnostic port on the OBD cars or the OBD-II port under dash and inspecting the data from user selected data list.
Even though this tool is for inspection of the ECM, you really need to know what you are doing with this tool.
What year is your car? If it is 96 up then it is OBDII and you can get an OBDII reader and it will tell you when you go into closed or open loop. I ran a TRD thermo on my 96 S/C'ed 4Runner and it would run about 170 deg on the 160 thermo and would always go into closed loop.