P0223
PowertrainThrottle Position Sensor/Switch B Circuit High Input
Usually a small job, often just a connector or a tired sensor, but you shouldn't ignore it because it can drop the car into limp mode without much warning. The ECU is seeing too high a voltage from throttle position sensor B (or accelerator pedal sensor B on drive-by-wire cars). Most modern throttles and pedals carry two sensors that should track each other in opposite directions, so when one of them reads higher than the safe window, the ECU stops trusting it and pulls power back to keep things safe.
ⓘ Information only. This page provides general educational information about fault code P0223. We do not assess the urgency or safety implications of any specific fault. That requires in-person diagnosis by a qualified mechanic. Full terms.
Recommended next steps
Whether a fault is urgent, drivable, or routine depends entirely on the cause on a specific vehicle, and that can only be determined by a qualified mechanic with diagnostic equipment. If a warning light is illuminated, the most reliable next step is professional diagnosis.
What does P0223 mean?
P0223 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Throttle Position Sensor/Switch B Circuit High Input.
This is a standardised OBD-II code. The technical definition is the same regardless of the make or model of vehicle, although specific causes and symptoms can vary between vehicles.
Symptoms commonly associated with this code
Symptoms that drivers often report alongside this code. Not all may apply to every case:
- • Engine warning light on, sometimes with a flashing limp mode or amber spanner symbol
- • Throttle feels dead or laggy, you press the pedal and nothing much happens for a moment
- • Sudden drop into reduced power mode, often capped at low revs until you restart
- • Stalling at idle or when you lift off at junctions
- • Cruise control and any adaptive cruise refusing to engage
- • On autos, lazy or jerky shifts because the box doesn't trust the throttle signal
Possible causes
Causes commonly associated with P0223, listed in approximate order of typical investigation. The actual cause on a specific vehicle can only be confirmed by professional diagnosis.
- 1. Corroded or backed-out pins in the pedal or throttle connector, the most common cause and the cheapest to sort. Damp gets into these connectors over the years
- 2. Failing throttle position or accelerator pedal sensor B, the internal track wears and the voltage drifts out of range
- 3. Chafed or shorted wiring in the loom, often where it flexes near the pedal box or runs along the inlet
- 4. Water ingress into the harness or sensor body, very common on cars parked outside or after a footwell soaking from a blocked scuttle drain
- 5. Faulty throttle actuator on electronic throttle bodies, where the motor and sensor pack live together
- 6. Carbon clogging a mechanical throttle body affecting the sensor sweep, less likely on a pure pedal sensor fault
- 7. A duff ECM, rare, and only after everything upstream checks out clean
How mechanics typically diagnose
A typical diagnostic sequence used by mechanics, provided here for educational reference only. Diagnostic work should be performed by a qualified mechanic with the appropriate tools and training.
- 1. Read live data and watch both throttle/pedal sensor voltages as you sweep the pedal. Sensor B should rise smoothly without spikes or dropouts. A reading pinned high or jumping to 5V tells you it's a signal fault, not a mechanical one
- 2. Unplug the sensor connector and check the pins for green corrosion, spread terminals, or moisture. Wiggle the loom with the engine running and watch the live data for the voltage to flicker
- 3. Back-probe the sensor with a multimeter and compare the reading against the workshop spec, most of these sensors sit somewhere between 0.5V closed and around 4.5V wide open
- 4. Check the 5V reference and earth at the connector. A poor earth makes a healthy sensor read high, so confirm the supply before you condemn the part
- 5. Run a bi-directional throttle sweep on the scan tool if the car supports it, to confirm the actuator and sensor agree
- 6. Clear the code and road test, watching for the voltage to climb out of range again so you know the repair actually held
Common questions about P0223
Can I just clean the connector and sort it myself? +
Often yes, and it's the first thing I'd try. Pull the pedal or throttle connector, look for corrosion or a pin that's pushed back in the housing, give the terminals a clean with contact cleaner and a soft brush, then reseat it firmly. If the live data voltage settles down after that, you've found it. Cleaning a mechanical throttle body can help if the sweep is gummed up, but on a lot of modern cars you'll need a relearn afterwards or the throttle won't sit right, so check what your car wants before you go in.
If I just clear the code, will it stay gone? +
Only if you've actually fixed something. Clear it on a car with a corroded connector or a worn sensor and it'll come back, sometimes within a few miles, sometimes after the next damp morning. Clearing is useful as a test once you've made a repair, to see if the fault returns. As a fix on its own it does nothing, the ECU just resets the limp mode counter and trips again the moment it sees the high voltage.
What's the risk if I leave it and keep driving? +
The main one is limp mode kicking in when you least want it. The car can cut to low power on a slip road or roundabout, which is dangerous when you're trying to merge with traffic. You may also get random stalling at idle. It won't usually leave you stranded, but a throttle fault that drops power mid-manoeuvre is the kind of thing that catches people out, so get it looked at rather than living with it for weeks.
Information only, not professional advice
The information on this page is provided for general guidance and educational purposes only. It is not a substitute for diagnosis or repair advice from a qualified mechanic. Always verify any fault before paying for repairs. carfaultcodes.co.uk accepts no liability for decisions made based on this information. Full terms →