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P2123Throttle/Pedal Position Sensor/Switch "D" Circuit High

What it means

The accelerator pedal position sensor signal voltage is higher than the sensor can normally produce (close to 5 V). Most often the signal wire or the sensor ground is open, or the signal is shorted to a supply voltage.

Symptoms

  • Limp mode or no response to the pedal
  • Engine stays at a fixed rpm
  • Electronic throttle warning light

Common causes

  • Open signal wire (the ECU's pull-up then reads high)
  • Open or high-resistance sensor ground
  • Signal shorted to the 5 V reference or to battery voltage
  • Failed accelerator pedal position sensor

What to check first

  1. Measure the voltage drop on the sensor ground with the key on (should be under 0.1 V)
  2. Unplug the sensor: the live data should jump to the opposite extreme
  3. Inspect the harness for chafing against other wires or hot parts
Can I drive with P2123? Not recommended. P2123 can lead to stalling, limp mode or engine damage; diagnose it before driving further.

Generic OBD-II meaning. Manufacturer-specific meanings and checks can differ; always check the service information for the car.

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P2123: questions and answers

What does P2123 mean?

P2123: Throttle/Pedal Position Sensor/Switch "D" Circuit High. The accelerator pedal position sensor signal voltage is higher than the sensor can normally produce (close to 5 V). Most often the signal wire or the sensor ground is open, or the signal is shorted to a supply voltage.

What are the symptoms of P2123?

Limp mode or no response to the pedal. Engine stays at a fixed rpm. Electronic throttle warning light.

What causes P2123?

Open signal wire (the ECU's pull-up then reads high). Open or high-resistance sensor ground. Signal shorted to the 5 V reference or to battery voltage. Failed accelerator pedal position sensor.

How do you diagnose P2123?

1. Measure the voltage drop on the sensor ground with the key on (should be under 0.1 V) 2. Unplug the sensor: the live data should jump to the opposite extreme 3. Inspect the harness for chafing against other wires or hot parts

Can I drive with P2123?

Not recommended. P2123 can lead to stalling, limp mode or engine damage; diagnose it before driving further.