Share a caseSign in
Air intakeSeverity High: diagnose before driving on

P0123Throttle/Pedal Position Sensor/Switch "A" Circuit High

What it means

The throttle or 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 with very limited power
  • Hesitation, surging or erratic idle
  • 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 throttle or 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 P0123? Not recommended. P0123 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.

How to test the parts behind P0123

Throttle and accelerator pedal position sensorsWiring, typical values, multimeter and scope tests

Cases with P0123 (0)

Share yours

No published cases with this code yet.

Colleagues asking about P0123

Ask for help

Stuck on P0123? Describe what you measured and ask the community.

P0123: questions and answers

What does P0123 mean?

P0123: Throttle/Pedal Position Sensor/Switch "A" Circuit High. The throttle or 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 P0123?

Limp mode with very limited power. Hesitation, surging or erratic idle. Electronic throttle warning light.

What causes P0123?

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 throttle or pedal position sensor.

How do you diagnose P0123?

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 P0123?

Not recommended. P0123 can lead to stalling, limp mode or engine damage; diagnose it before driving further.