Heat Sensor #2 Code in 97 Camry 6cyl 194k miles

I have a 97 Toyota Camry. I have a diagnostic tool at work that gave an error code on the #2 Heat Sensor. I reset the code, but after the next drive cycle the "Check Engine" light came back on again, showing the same error. Do you have any idea as to what physical thing could be causing this code?
Thank you guys in advance!
BTW, Someone told me it might be my thermostat?

What was the code?