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.
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.
Related codes
Often seen with P0123
Read & clear P0123 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX