P0123

Throttle/Pedal Position Sensor/Switch A Circuit High

Throttle / pedal position Generic OBD-II High

What it means

P0123 means the throttle position (or accelerator pedal) sensor "A" is sending an abnormally high voltage signal — higher than the ECM expects even at closed throttle. Because this sensor tells the engine how far the throttle is open, a bad reading can cause surging, hesitation, reduced power, or the car dropping into a safe "limp" mode.

High

Can I keep driving? Not recommended — a throttle/pedal position fault often triggers reduced-power or limp mode and unpredictable throttle response; drive as little as possible until it's fixed.

Real-world scan data

Seen in

5,700

scans in the past year

Found in

0.9%

of scans

1.6%

of scans that found faults

Appears alongside · share of P0123 scans

P0222in 48.0% of scans

P0113in 17.8% of scans

P0108in 16.1% of scans

Figures reflect only diagnostic scans recorded through our own apps and tools. Cars are typically scanned because a symptom or warning light prompted it, so these counts describe our scan records — not the incidence of faults in any model, and not the quality, reliability, or safety of any vehicle. No comparison between manufacturers or models is implied. All trademarks belong to their respective owners; no affiliation or endorsement is implied.

Common symptoms

What you'll notice

Check-engine light on
Reduced engine power or limp mode
Surging, hesitation, or erratic idle
Poor or unpredictable throttle response
Hard starting or stalling in some cases

Common causes

Most likely first

Faulty throttle position / accelerator pedal position sensorLikely
Signal wire shorted to voltage, or an open ground in the circuitCommon
Corroded or loose sensor connectorCommon
Damaged wiring harnessLess often
Rarely, an ECM faultLess often

How to diagnose & fix

Work through it in order

Read live throttle/pedal data and watch for the signal reading high or pegged.
Inspect the sensor connector and wiring for shorts to power, opens, or corrosion.
Back-probe the sensor's reference, signal, and ground voltages against spec.
Replace the throttle position / pedal sensor if the signal stays high with good wiring.
Clear the code, relearn throttle if required, and re-test.

FAQ

Quick answers

Is it safe to drive with P0123?+

Not really. The car may drop into limp mode or respond unpredictably to the pedal, which is unsafe. Have it fixed before extended driving.

Can I just clear P0123?+

Clearing it won't fix a shorted circuit or failed sensor — the code and the limp-mode behaviour will return.

Read & clear P0123 yourself

Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.

▶ Get it on Google Play

✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX