Description of DTC code P0120

The TPS Sensor (Throttle Position Sensor) is located above the throttle. This sensor detects the angle of the throttle blade. When the pedal accelerator moves, the Throttle Position Sensor (TPS) sends a signal to the Powertrain Control Module (PCM).

The TPS sensor has 3 wires, two from the PCM to the TPS, which are the reference voltage (5 volts) and ground. The other cable goes from the TPS sensor to the PCM and this is a signal return. The Throttle Position Sensor notifies the PCM of the throttle position via the signal cable. When the throttle is closed, the signal is approximately 0.45 volts, and when the throttle is fully depressed, the signal voltage will be close to 5 volts.

If the Powertrain Control Module (PCM) observes that the voltage is not within specification during normal operation, the DTC code P0120 OBDII is set.

Symptoms of fault code P0120

  • Check Engine light is on.
  • Idle failure.
  • Maybe, it starts the engine and in a short time, it stops.

Causes of OBD2 P0120

When the diagnostic code P0120 OBD2 is set, it means that one or more of the following issues has occurred:

  • Accelerator Position Sensor (TPS) circuit cables may be defective.
  • Corrosion on the connector of the Throttle Position Sensor (TPS)
  • The TPS sensor may be defective.

Possible solutions of the DTC code P0120

When the fault code P0120 OBDII is set, you must follow these steps to correct the problems caused by it:

  • By using an automotive scanner, with the key in the on position and the engine off, watch the voltage of the TPS sensor. With the throttle closed, the voltage should be between 0.45 volts. It should then increase to 4.5 or 5 volts as you accelerate. If you notice problems with the TPS sensor sweep voltage, you should change it.
  • Note that if the throttle is closed, the voltage must be approximately 0.45 volts, if not or the voltage sticks, you must unplug the Throttle Position Sensor connector. Then, with the key in the ignition position and the engine off, check that the 5-volt reference is present in the connector. In the same way, check that there is a good ground.
  • Check for continuity in the signal circuit. To do this, fuse a cable between the ground circuit of the TPS connector and the signal circuit. In case the TPS reading displays 0, you should perform an inspection on the signal cable as there is most likely a short. If you find defective wires, replace them.

Codes related to P0120

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