The meaning of the code P1516 Chevy Silverado 2003 remains the same for this model. In fact, this is the issue that mainly occurs with the Silverado model of 2003. Basically, this P1516 is a sensor that scans the throttle position. It's much like a car's computer that prevents the vehicle from going overdriven by alerting. Two circuits determine and execute the throttle control according to how far you push the gas. These two pieces of equipment take direct control of the throttle and ensure the correct position of TAC according to your steering. But when the position goes wrong, the code shows up.