1996 Chevy Truck Throttle Position Sensor

Check engine light came on, and it was coded - showed that the throttle position sensor was bad. Had it replaced and a couple of hours later the light came back on. Once again the code showed that the throttle sensor was bad - had it replaced for the second time. Two days later, the light is back on and the code shows that the throttle sensor is bad, again. Occasionally, the check engine light will go off, and the pickup runs great - then the light comes back on.