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P2122Throttle/Pedal Position Sensor/Switch "D" Circuit Low

What it means

The accelerator pedal position sensor signal voltage is lower than the sensor can normally produce (usually below about 0.2 V on a 0–5 V sensor). Most often the signal wire is shorted to ground or the 5 V supply is missing.

Symptoms

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

Common causes

  • Signal wire shorted to ground or chafed through
  • 5 V reference open, or pulled down by another faulty sensor on the same supply
  • Failed accelerator pedal position sensor
  • Water or corrosion in the connector

What to check first

  1. With the key on, measure the 5 V reference at the connector (about 4.8–5.1 V)
  2. Back-probe the signal and watch it while wiggling the harness
  3. Unplug sensors that share the 5 V reference one at a time and see whether the supply recovers
Can I drive with P2122? Not recommended. P2122 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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P2122: questions and answers

What does P2122 mean?

P2122: Throttle/Pedal Position Sensor/Switch "D" Circuit Low. The accelerator pedal position sensor signal voltage is lower than the sensor can normally produce (usually below about 0.2 V on a 0–5 V sensor). Most often the signal wire is shorted to ground or the 5 V supply is missing.

What are the symptoms of P2122?

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

What causes P2122?

Signal wire shorted to ground or chafed through. 5 V reference open, or pulled down by another faulty sensor on the same supply. Failed accelerator pedal position sensor. Water or corrosion in the connector.

How do you diagnose P2122?

1. With the key on, measure the 5 V reference at the connector (about 4.8–5.1 V) 2. Back-probe the signal and watch it while wiggling the harness 3. Unplug sensors that share the 5 V reference one at a time and see whether the supply recovers

Can I drive with P2122?

Not recommended. P2122 can lead to stalling, limp mode or engine damage; diagnose it before driving further.