What is the p0121 code for the chevy silverado?

When a Chevy Silverado displays the error code p0121, it usually means that there is something wrong with the throttle position sensor. This code is triggered when there is difficulty or complete failure in transmitting data to the Powertrain Control Module (PCM) through the throttle sensor. Typically, the throttle sensor transmits messages through its A circuit and so, this may also indicate an electrical issue within the circuit. The extent to which this can impact Your vehicle is hard to gauge without performing a complete diagnostic test. If Youre seeing Your engine fail constantly, or become tight when the car is idling, it could indicate that the throttle sensor has completely failed. As a result, its a good idea to tend to any TPS issues as soon as possible.