P0221
Throttle/Pedal Position Sensor/Switch B Circuit Range/Performance.
- Generic
- Powertrain
- Generic code
- Medium severity
How this code is built
- P
- SystemPowertrain
- 0
- Defined bySAE, the same on every car
- 2
- AreaFuel and air metering (injector circuit)
- 21
- FaultThe specific fault in that area
What it means
P0221 means the engine control unit has found that the signal from throttle or pedal position sensor B is out of range or does not agree with what it expects. It usually compares sensor B with sensor A (or with the commanded throttle angle and airflow) and sets the code when the two do not correlate plausibly. The exact sensor layout and logic vary by model and engine.
Symptoms
- Engine warning light on
- Reduced power or limp-home mode with limited throttle response
- Hesitation or poor, uneven acceleration
- Unstable or high idle, or stalling at idle
- Throttle response feels delayed or jerky
- Cruise control or traction control unavailable
Possible causes
- Faulty or worn throttle position sensor or accelerator pedal sensor (track B drifting out of range)likely
- Wiring faults to sensor B: chafed, open or high-resistance wires, or short to supply or earthlikely
- Corroded, loose or damaged connector terminals at the throttle body or pedal assemblylikely
- Dirty or carbon-fouled throttle body causing the throttle to stick or not match its commanded positionpossible
- Poor reference voltage or earth supply to the sensorspossible
- Throttle motor or throttle body mechanical fault, or a throttle adaptation that has been lost or not relearnedpossible
- Fault within the engine control unit itselfrare
How to diagnose
- Read all stored and pending codes and the freeze frame data, noting load, rpm and throttle values when the code set. Check for related throttle, pedal or reference voltage codes.
- Check the manufacturer's information for which component 'B' refers to on this model (throttle body sensor or pedal sensor).
- Inspect the throttle body and pedal assembly wiring and connectors for damage, water ingress, corrosion and loose pins.
- With live data, compare sensor A and B readings as the pedal is pressed slowly from rest to full, looking for jumps, dropouts or readings that do not track each other.
- Check the throttle body for carbon build-up and free movement of the plate, without forcing it.
- Measure the reference voltage and earth at the sensor connector against the model's specification.
- Check the wiring between sensor and control unit for continuity and shorts, with the connectors disconnected and the ignition off.
- Test the suspect sensor or throttle body against specification, or substitute with a known good one if the manufacturer allows.
How to fix
- Repair or replace damaged wiring and clean or repair connector terminals.
- Replace the faulty accelerator pedal assembly or throttle body, depending on which sensor is at fault.
- Clean the throttle body using a suitable method for the model, then carry out the throttle adaptation or relearn procedure.
- Restore correct reference voltage and earth supplies by repairing the circuit fault found.
- Only if the manufacturer lists it as a known cause, update the control unit software to the latest calibration.
Can I keep driving?
Medium severity
The car may enter limp-home mode with reduced power, which can be unsafe when pulling out or overtaking. Drive cautiously only as far as needed and get it checked soon.
Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.