P0120: Throttle/pedal position sensor/switch "A" circuit
The engine computer gets a missing, out-of-range or erratic signal from a throttle or accelerator pedal position sensor. Depending on the car, sensor “A”, “B” or “C” is on the throttle body or in the pedal. The engine computer often limits the power (limp mode).
Updated
What P0120 means
On most modern cars there’s no cable between the accelerator pedal and the engine. Sensors in the pedal tell the engine computer how far you press it, and a motor opens the throttle, with its own sensors reporting its position. Older cars with a throttle cable have a single throttle position sensor.
The positions are measured by two or more sensors, named “A”, “B”, “C” and so on. Which letter is in the throttle and which in the pedal depends on the car: the service information for your car says.
P0120 means the signal of sensor “A” is missing or out of its normal range. Because this controls the power, the engine computer often switches to limp mode: limited power, or only idle.
P0121 to P0124 and P0220 to P0229: the other faults and sensors
P0121 means the signal is there but implausible, P0122 that it’s too low, P0123 too high and P0124 that it drops out. P0220 to P0224 are the same faults for sensor “B”, and P0225 to P0229 for sensor “C”. The causes and advice are the same. When codes for two sensors appear together, a supply, earth or connector they share is more likely than two faulty sensors.
P0121: Throttle/pedal position sensor/switch "A" circuit range/performance
P0122: Throttle/pedal position sensor/switch "A" circuit low
P0123: Throttle/pedal position sensor/switch "A" circuit high
P0124: Throttle/Pedal Position Sensor/Switch A Circuit Intermittent
P0220: Throttle/Pedal Position Sensor/Switch B Circuit
P0221: Throttle/Pedal Position Sensor/Switch B Circuit Range/Performance
P0222: Throttle/Pedal Position Sensor/Switch B Circuit Low
P0223: Throttle/Pedal Position Sensor/Switch B Circuit High
P0224: Throttle/Pedal Position Sensor/Switch B Circuit Intermittent
P0225: Throttle/Pedal Position Sensor/Switch C Circuit
P0226: Throttle/Pedal Position Sensor/Switch C Circuit Range/Performance
P0227: Throttle/Pedal Position Sensor/Switch C Circuit Low
P0228: Throttle/Pedal Position Sensor/Switch C Circuit High
P0229: Throttle/Pedal Position Sensor/Switch C Circuit Intermittent
Can I keep driving?
Drive gently
Drive gently and only as far as you need to, and have it checked soon. The engine computer may cut the power (limp mode) or let the engine only idle, sometimes suddenly, so avoid motorways and overtaking until it’s fixed. If the engine stalls, or doesn’t respond to the pedal as it should, stop when it’s safe to do so and have it recovered.
General guidance based on the code alone, not on the car’s actual condition. If in doubt, stop and ask a mechanic.
Limp mode can come on suddenly, for example while overtaking or joining a motorway, so avoid those until it’s fixed.
Symptoms
- Limp mode: less power, or the engine won’t rev above a limit.
- Hesitation or jerking, or an idle that’s too high or uneven.
- Stalling on some cars.
- Cruise control not working on some cars.
Common causes
- Faulty throttle or pedal position sensor. With an electronic throttle, the sensors are usually part of the throttle body or the pedal assembly, which is then replaced as a unit.
- Wiring or connector fault. Check for loose, corroded or damaged plugs at the throttle body and the pedal.
- Dirty or sticking throttle body. Carbon can stop the throttle moving freely, so its position no longer matches what the engine computer expects.
- Fault in the sensor’s supply or earth. The sensors share a supply, sometimes with other sensors too. A fault there sets codes for several sensors at once.
Typical fixes
- Read all fault codes: several sensor codes together point to a shared supply, earth or connector.
- Check the plugs at the throttle body and the pedal for corrosion and a firm fit.
- Have the throttle body checked for carbon and cleaned if needed, with a cleaner made for it.
- Have the sensor signals checked with a diagnostic tool while the pedal is pressed slowly, and replace the faulty part. Some cars then need a throttle or pedal relearn, with a tool for the make.
Questions
Can I drive with P0120?
Gently, and only as far as you need to. The engine computer may cut the power or let the engine only idle, sometimes suddenly, so avoid motorways and overtaking. If the engine stalls or doesn’t respond to the pedal as it should, stop when it’s safe to do so and have it recovered.
Is P0120 the throttle or the accelerator pedal?
It depends on the car. Sensor “A” is on the throttle body on some cars and in the pedal on others. The service information for your car says which.
Can cleaning the throttle body fix it?
Sometimes, when carbon stops the throttle from moving freely. If the code points to a circuit fault (low, high or intermittent), check the wiring and connectors first.