Error code

OBD2 P0121

OBD2P0121
Diagnostic Trouble Code· Standard OBD-II fault code read from the vehicle's onboard diagnostics.

What it means

Throttle/Pedal Position Sensor/Switch 'A' Circuit Range/Performance.

Severity

moderateCan drive, but performance issues may occur.

Summary

P0121 indicates that the throttle position sensor (TPS) or accelerator pedal position sensor 'A' is not performing within expected parameters, typically due to range or performance issues.

Symptoms

  • Hesitation or stumbling upon acceleration
  • Unstable idle
  • Illuminated check engine light

Common Causes

  • Faulty TPS sensor
  • Open or shorted TPS circuit
  • PCM malfunction

Diagnosis

  1. Visually inspect the sensor and its wiring for damage or corrosion
  2. Check throttle body assembly for binding or contamination
  3. Test the TPS using a multimeter to check voltage readings at idle and wide open throttle positions

Fixes

  • Replace faulty TPS sensor

FAQ

What should I do if the visual inspection doesn't reveal any issues?

Proceed to test the TPS with a multimeter or scan tool, and check the circuit wiring for power and ground.

How can I clean the throttle body assembly?

Use throttle body cleaner available at auto parts stores. Clean it thoroughly and reinstall before clearing codes.

View source

Not affiliated with OBD2. Answer summarized from the manufacturer's manual linked above; consult that source for the authoritative procedure.

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