Description of DTC code P2121

The Throttle Position Sensor (TPS) measures the amount of throttle opening. As the throttle opens, the reading increases, and this is measured in volts. This sensor gets 5 volts of reference and a ground signal from the Powertrain Control Module (PCM).

If the PCM finds the throttle angle is above or below what is expected for the current engine rpm, the DTC P2121 OBDII code will be set, and the Check Engine light illuminates. The letter "D" means a particular circuit or circuit area.

Symptoms of fault code P2121

  • Malfunction Indicator Lamp (MIL) ON.
  • The motor does not start.
  • Problems during acceleration.
  • A large amount of black smoke comes out of the exhaust when accelerating.

Causes of OBD2 P2121

Reasons for setting the P2121 OBD2 diagnostic code:

  • Perhaps the Throttle Position Sensor internally is shorted or has an open circuit.
  • The system wires could have deficiencies that cause a short.
  • The TPS sensor connector may be corroded.

Possible solutions of the DTC code P2121

To troubleshoot the P2121 OBDII error code, try this:

  • Check the Throttle Position Sensor for 5 volts reference voltage and a good ground connection. Also, check the signal circuit for 12 volts. If so, it is due to a short. Repair if necessary.
  • Check TPS Sensor connector for corrosion. Repair if necessary.
  • Use a scanner to observe the Throttle Position Sensor readings at idle and wide-open throttle. The results should match the manufacturer's specifications. If there is a narrow range of differences, replace the TPS Sensor.
  • With an oscilloscope, observe the signal from the TPS Sensor, which should sweep up and down without jumps. If there are problems with the signal, manipulate the wires and look for changes in the pattern. If it drops, replace the TPS sensor.

Codes related to P2121

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