Camry :: 2005 - Error Codes P0128 And B1771

Car's a 2005 SE I4, auto, US-made

So, I finally got the Techstream to work; I think. I had ordered one which never came, then ordered a second one, which showed up after some five weeks. It took some playing around with the software, but it seems that I finally got it to work tonight on my old, and slow, Dell laptop (Windows 7, 32-bit), which will be devoted purely to car diagnostics, since there are supposed trojan viruses in the software.

The car's temperature gauge had been running very low, I had lost top-end power, as in, hitting a wall at 80-85 mph+ where there was no acceleration despite the pedal being floored, and eventually the check engine light came on. After the light came on, I took it easy on the car and ordered the software and cable. In full disclosure, I did a complete coolant flush in late Summer/early Fall, 2015, pouring in the proper fluid. There are no leaks and the level is correct. There are no foul odors from the engine. There is a slight head gasket leak on the upper right hand corner which I plan to address when the temps warm up again (no codes pertaining to vacuum leaks).

Tonight I managed to use the software and cable for the first time and pulled the following codes:

Engine and ECT, Monitor Status COM, DTC (Code) P0128

Occupant Detection, Monitor Status None, DTC (Code) B1771

So, do the symptoms described above, including loss of power, "match" the bad thermostat diagnosis?