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P2120 OBD-II Trouble Code: Throttle/Pedal Position Sensor/Switch D Circuit

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P2120 trouble code definition

Throttle/Pedal Position Sensor/Switch D Circuit

What the P2120 code means

P2120 is an OBD-II generic code for the engine control module (ECM) detecting a major failure in the throttle pedal position sensor circuit of a below or above specified voltage return from the sensor.

What causes the P2120 code?

The ECM is getting a voltage return from the throttle pedal position sensor of below .24 volts or above 4.49 volts, indicating the throttle position sensor is not within specification and causes the ECM to go into failure management mode for limited throttle opening.

What are the symptoms of the P2120 code?

  • The Check Engine Light will be illuminated and the code is set in ECM memory as a fault.

  • The engine will have limited acceleration and slow throttle response and RPM will be limited.

  • Depending on the failure mode entered and manufacturer will depend on other symptoms encountered like idle only or limited power and throttle opening.

How does a mechanic diagnose the P2120 code?

  • Scans and documents the code in the ECM to check the freeze frame data for failure

  • Diagnoses the code as per the manufacturer's pinpoint test

  • Checks the scan data of the throttle position sensor to see if it is getting the proper reference voltage and is sensing the throttle angle properly.

Common mistakes when diagnosing the P2120 code

  • Clearing ECM memory codes before checking the freeze frame data for the main failure problem, so that the failure may be duplicated and repaired.

  • Failing to clear the ECM codes after the codes are fixed

How serious is the P2120 code?

Code P2120 is an indication that the ECM detects a major throttle position failure and is in failure management mode. This has limited the RPM that the engine can go since the throttle control actuator system depends on the pedal position sensor for proper control of the throttle.

What repairs can fix the P2120 code?

Additional comments for consideration regarding the P2120 code

Code P2120 is major failure of the throttle control circuit and the vehicle may only idle and not allow any throttle control at all.

Need help with a P2120 code?

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The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
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