97 Camry with Diagnostic code: P0773

You got the first two steps correct in scanning for the trouble codes and finding out how to check the shift solenoid circuit.

The next step is to check the circuit as described in the articles you found.

If the transmission fluid hasn't been changed in a long time, then the car may need a transmission service, but that is unlikely to cure the problem, which is an electrical problem.

I remember getting the same problem on a 1998 RAV4. It wasn't a check engine light but the O/D ON/OFF indicator kept blinking. I brought it to the dealer and they told me of this same circuit. I religiously changed my A/T fluid, but still the circuit failed, and changing the fluid wont do anything. I can't tell you how I got it fixed since I sold the car without fixing it.

It's probably the gas. I posted to this group about the check engine light. It came on in the fall of 2007 when the gas company's switched to winter blend and stayed on all winter. Auto zone said it was a faulty O2 sensor. I could not afford to replace. Spring came, the ga companies switched back to summer blend, the light went out and has stayed out all summer. Just my 2cents.

Fuel quality will not affect the performance of a shift solenoid.

The code is for failure of the torque converter clutch solenoid electrical circuit. However, I've learned to be very wary of Japanese and Korean codes concerning electrical failure. You can be fairly sure of a TCC problem, but it might not be electrical.

I had the same thing on a 1999 Lexus ES 300. It throws that code in spells. The car runs and shifts fine. It's been about 25K miles since the first appearance and I have not seen it in quite awhile now. The dealer said the transmission needs overhauling. I'll just run it until it quits. The lights go out, like you said after a few miles or start and stops.