engine code P0121

Question

Silverado 2008 engine light on, code P0121. What does code mean?

Answer 1

The Throttle Position Sensor/Switch is located on the Throttle Body of the Intake Manifold and the Pedal Position Sensor/Switch is part of the Accelerator Pedal assembly. These sensors provide precise input from the driver's foot in terms of how MUCH power is needed from the engine and, how URGENTLY power is needed.  As the Throttle Position Sensor is rotated from its base resting position to full acceleration, typically, it sends an increasing voltage signal to the Powertrain Control Module (PCM). This increasing or decreasing voltage signal is used by the PCM to manage the Air Fuel Ratio and Spark Timing of the engine as well as other Emissions System Components.

Code P0121 triggers when the Throttle/Pedal Sensor/Switch "A" Circuit sends irrational data to the PowerTrain Control Module or PCM.  

This code can be an issue with the throttle positions sensor or with the pedal position sensor. Check and make sure the connection at the gas pedal is clean and tight.