P0120P0124

P0120P0124 refers to a group of OBD-II diagnostic trouble codes that indicate issues with the throttle position sensor (TPS) circuit in a vehicle. These codes are related to the signal supplied by the TPS to the engine control unit (ECU) and can affect engine idle, acceleration, and overall driveability. The range P0120 through P0124 covers different aspects of the TPS circuit performance and input.

The individual codes are commonly defined as follows: P0120 Throttle Position Sensor/Switch A Circuit Malfunction; P0121 Throttle Position Sensor/Switch A Circuit Range/Performance Problem; P0122 TPS Circuit Low Input; P0123 TPS Circuit High Input; P0124 Throttle Position Sensor/Switch A Circuit Range/Performance. While wording varies by manufacturer, all indicate a problem in the TPS circuit or its communication with the ECU. In some vehicles, there may also be a “B” sensor or additional TPS related codes.

Typical causes include a faulty TPS, damaged or corroded wiring or connectors, a faulty 5-volt reference or ground to the sensor, or mechanical binding or contamination in the throttle body. Symptoms can include check engine light, poor or inconsistent acceleration, surging or stalling, rough idle, or unintended changes in engine speed.

Diagnostic steps generally involve retrieving the codes with a scan tool, inspecting the TPS wiring and connectors, and testing the sensor with a multimeter or oscilloscope. Common tests include verifying a smooth, linear voltage change from the TPS (often about 0.5 V at idle to near 5 V at wide-open throttle) and ensuring the reference voltage and ground are stable. If the TPS and wiring check out, cleaning or replacing the throttle body or TPS may be required, followed by rechecking for codes. If symptoms persist, further ECU diagnostics may be necessary.