1995 Camry CEL code 52

I have a 1995 Camry 2.2 automatic with 220,700 miles on it. The car is in great shape and I picked it up cheap for my 16 year old daughter. The guy I bought this car off of rebuilt the top end of the motor at 213,000 miles because the car had been overheated. It runs great but gets poor fuel economy. It also throws a check engine light once you start driving (not just running - you can rev the engine in park and there is no check engine). I flashed the codes and got a 52 from the check engine and a 63 from the O/D off light. I believe the transmission code 63 is "shift solenoid #2" and the CEL code 52 is "knock sensor". My question is: is it possible that the knock sensor really is bad? I always heard that knock sensors don't go bad and if you get a code you have a knock. I don't hear any knocking from the engine and since the light doesn't come on until the car is moving (usually about the first time it shifts to second) I believe it is the shift solenoid problem turning it on. The poor fuel economy leads me to believe that there may be a problem with something else and since that knock sensor code is present that might just be it. What do you think?