P0222
PowertrainThrottle Position Sensor/Switch B Circuit Low Input
The ECM watches the voltage coming back from throttle position sensor circuit B, and on a healthy system that signal sits within a known band as the throttle moves. When that voltage drops below the expected floor, often near zero when it should be reading higher, the ECM logs P0222 and assumes it can no longer trust the throttle reading. For you as the driver, that usually shows up as the car dropping into a reduced-power limp mode to keep things safe, because the computer would rather hobble home than guess at how far you've pressed the pedal.
ⓘ Information only. This page provides general educational information about fault code P0222. 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 P0222 mean?
P0222 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Throttle Position Sensor/Switch B Circuit Low 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 the throttle/EPC light alongside it
- • Car drops into limp mode, capped at maybe 2,000-3,000 rpm with sluggish pull
- • Accelerator feels dead or laggy, you press and nothing much happens for a beat
- • Rough or hunting idle, and the odd stall when you come to a stop
- • Hesitation or a flat spot when you try to accelerate
- • Harder to start on some cars, particularly when cold
Possible causes
Causes commonly associated with P0222, listed in approximate order of typical investigation. The actual cause on a specific vehicle can only be confirmed by professional diagnosis.
- 1. Faulty throttle position sensor itself, the internal track wears or the second channel fails and drops the voltage low
- 2. Corroded or loose pins in the throttle body connector, very common on cars that have seen damp and road salt
- 3. Chafed or broken signal wire between the throttle body and ECM, sometimes shorted to ground
- 4. Loss of the 5-volt reference feed to the sensor, which pulls the signal right down
- 5. Open circuit in the sensor earth, which can mimic a low signal
- 6. Failed accelerator pedal position sensor on drive-by-wire setups, since pedal and throttle data are checked against each other
- 7. Carbon and muck on the throttle body fouling the sensor's range, less common but worth a look
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 the TPS B voltage while you slowly open the throttle by hand, a stuck low or dead-flat reading points you straight at sensor or wiring rather than guesswork
- 2. Wiggle-test the throttle body connector with the ignition on while watching that voltage, if it jumps about you've found a dodgy pin or connection
- 3. Back-probe the connector and confirm you have a steady 5-volt reference and a good earth, no reference means the fault is upstream in the loom or ECM
- 4. Measure the sensor's own output against the manual figures, it should climb smoothly off its base reading and not collapse to zero
- 5. Inspect the loom from throttle body to ECM for rubbing points, breaks, and green corrosion, especially where it passes near hot or moving parts
- 6. Only after wiring and supply check out clean should you condemn the sensor or look at the ECM, swapping parts before this stage just burns money
Common questions about P0222
If I clear it, does it actually stay gone? +
Not if the fault is still there. P0222 is a hard electrical fault, so the moment the ECM sees that low voltage again it relogs the code, often within seconds of you starting up. You might get a brief honeymoon where the car drives normally before it drops back into limp mode. Clearing it is only useful as a test after you've fixed the wiring or sensor, to confirm it stays away.
What's the risk if I just leave it? +
You won't blow the engine, but you'll be stuck in limp mode with a hard rev cap, which is properly dangerous when you need a burst of power to pull onto a motorway or out of a junction. The car may also stall at idle without warning. It won't get better on its own and a frayed wire only gets worse with vibration and weather.
How quickly do I need to sort this? +
Treat it as a soon job rather than a roadside emergency. The car is drivable in limp mode for short local trips, but I wouldn't be doing motorway runs or long journeys with it. If it's stalling at junctions, get it looked at before you drive it much further.
Is it the sensor or just the wiring and plug? +
Plenty of P0222s turn out to be the connector or the loom rather than a dead sensor, particularly corroded pins or a chafed signal wire. That's exactly why the live-data and back-probe checks come first. Replacing the throttle body or sensor before you've ruled out the wiring is the classic way to spend a few hundred quid and still have the same code.
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 →