P0122 - Throttle/Pedal Position Sensor/Switch A Circuit Low Input

P0122 is triggered when the Engine Control Module (ECM/PCM) detects that the voltage signal from the Throttle Position Sensor (TPS) circuit 'A' is below the minimum calibrated limit, typically less than 0.2V to 0.4V. The TPS is a potentiometer that provides a variable voltage signal representing throttle plate angle. This input is critical for fuel strategy, ignition timing, and transmission shift points. When the signal drops too low, the system enters fail-safe or 'Limp Mode' to prevent unintended acceleration or engine damage, often disabling cruise control and limiting RPM.