P0120: Throttle or pedal position sensor A: circuit fault

What P0120 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 from sensor A is not valid.

Most common causes

• Sensor connector loose, dirty or corroded
• Sensor wires chafed, broken or with a poor earth
• Worn or faulty position sensor
• Faulty throttle body (on many cars the sensor is built into it)
• Fault in the supply the ECU feeds to the sensor
• 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 P0120?

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

With the ignition on and the engine off, watch the throttle or pedal position in live data while you press the accelerator very slowly: the value should rise smoothly, with no jumps or drops. If it jumps, gently wiggle the connector and see if it changes.

How to read and clear P0120 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 P0120 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

• P0116 Engine coolant temperature sensor range or performance
• P0117 Engine coolant temperature sensor circuit low
• P0118 Engine coolant temperature sensor circuit high
• P0119 Engine coolant temperature sensor circuit intermittent
• P0121 Throttle or pedal position sensor A: out of expected range
• P0122 Throttle or pedal position sensor A: low signal
• P0123 Throttle or pedal position sensor A: high signal
• P0124 Throttle or pedal position sensor A: intermittent signal
• 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

P0120 is a generic code, so it means the same on any make, for example on Audi, Fiat, Mazda, Peugeot, Toyota, Volkswagen. See what Final OBD does on your car in makes and models.