2000 chevy cavalier with error code p0122

Hi, my son has a 2000 chevy cavalier with 57,000 miles. About 2 months ago the engine light came on and we took it to get the code cleared. It was po122 TPS low voltage. They said it was the Trottle Possition Sensor was bad, so we replaced it. 2 days later the same code came on. I took it to a guy I know and he said the low voltage was cause by another sensor above the gas tank. He replaced it and it ran fine. Now the car is spitting and sputtering and the engine light came on again (po122). I had them clear the code at autozone and the car ran fine, but a day or two later the code comes on again and the car runs terrible. To my knowlege the TPS is not adjustable on a 2000. Any help, thanks in advance.!!!
 

A very common DIY mistake is incorrect installation of the TPS. It will 'go in', but have to turn in (slight spring pressure) before bolting down.