P0123: Throttle or pedal position sensor A: high signal

What P0123 means

The ECU needs to know how far the throttle valve (the flap that lets air into the engine) is open, or how far you are pressing the accelerator, to meter air and fuel. Which sensor counts as sensor A is decided by each manufacturer, although it is usually the throttle one. This code means the signal voltage is above what is possible, usually because of an electrical problem.

Most common causes

• Sensor connector loose, damp or corroded
• Sensor earth wire broken or loose
• Signal wire touching a supply wire
• Faulty position sensor
• Faulty throttle body (if the sensor is built in)
• Faulty engine ECU (uncommon)

Symptoms

• Engine warning light on
• The car goes into limp mode and barely accelerates
• Unstable idle or the engine stalling
• Jerking or odd response when you press the accelerator

Can you drive with P0123?

With care You can drive, but the car may suddenly lose power when it drops into limp mode. Get it to a garage soon and avoid overtaking and fast roads in the meantime.

How to check it

Check the sensor position in live data with your foot off the pedal: if it shows full travel or something impossible without pressing, suspect the sensor earth or the connector. Make sure the connector is fully home and free of moisture.

How to read and clear P0123 with Final OBD

Plug an OBD2 scanner in under the steering wheel, switch the ignition on and open Final OBD. Under Faults you’ll see P0123 with this same explanation and whether it’s confirmed, pending or permanent.

With Free you read this code with its short description for nothing, and clear it if the engine stores it over standard OBD. With Pro you get the full explanation, how the car was running when it was logged (revs, temperature, load) and clearing in every control unit.

Clearing the code only turns the light off: if the cause is still there, it comes back. Clear it once it’s fixed, and not right before the ITV. It’s all in how to read and clear fault codes and in the ITV and OBD.

Similar codes

• P0119 Engine coolant temperature sensor circuit intermittent
• P0120 Throttle or pedal position sensor A: circuit fault
• P0121 Throttle or pedal position sensor A: out of expected range
• P0122 Throttle or pedal position sensor A: low signal
• P0124 Throttle or pedal position sensor A: intermittent signal
• P0125 Engine takes too long to warm up for fuel mixture control
• P0128 Thermostat: coolant not reaching normal operating temperature
• P0130 Oxygen sensor (bank 1, sensor 1): circuit fault
• P0100 Mass or volume air flow sensor circuit fault
• P0101 Air flow sensor range or performance problem
• P0102 Air flow sensor circuit low input
• P0103 Air flow sensor circuit high input

P0123 is a generic code, so it means the same on any make, for example on BMW, Fiat, Ford, Mazda, Peugeot, Volkswagen. See what Final OBD does on your car in makes and models.