P0121 OBD II Trouble Code Throttle Position Sensor/Switch A Circuit Range/Performance Problem

Symptoms of P0121 OBD II Trouble Code

  • Malfunction Indicator Lamp (MIL) illumination (Check Engine Light or Service Engine Soon light)
  • Intermittent stumble on acceleration or deceleration
  • Blows black smoke on acceleration
  • No start

Common Causes of P0121 OBD II Trouble Code

  • TPS has intermittent open or short internally
  • Harness is rubbing and causing an open or short in the wiring
  • Bad connection at the TPS
  • Bad PCM (less likely)
  • Water or corrosion in connector or sensor