P0222
Throttle/Pedal Position Sensor/Switch B Circuit Low InputP0222 is a generic OBD-II powertrain diagnostic trouble code: Throttle/Pedal Position Sensor/Switch B Circuit Low Input. It is logged by the engine control unit when the throttle monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.
What P0222 means
P0222 is stored when the PCM detects that the voltage signal from the throttle position sensor (TPS) or accelerator pedal position (APP) sensor "B" circuit is persistently below the manufacturer's minimum calibrated threshold — typically below approximately 0.5 V when the throttle is closed or the pedal is released. In a correctly functioning drive-by-wire system, the B-channel voltage should rise smoothly from around 0.5 V at idle to approximately 4.5 V at wide-open throttle (or follow an inverse curve depending on the vehicle platform). A stuck-low reading suggests the signal wire is open-circuited, shorted to ground, the sensor has failed internally, or the ECM's reference voltage supply is absent.
Because a voltage of zero (or near-zero) on the B-channel could theoretically also represent a fully closed throttle, the PCM cross-checks the B-channel against the A-channel and against expected idle conditions. When B remains at minimum regardless of pedal position — especially when A-channel indicates increasing throttle — the PCM flags P0222 and initiates a protective limp-mode strategy. The engine may be limited to a forced idle or a very low power ceiling to prevent uncontrolled vehicle acceleration.
P0222 shares its root cause space with P0222's sibling codes: P0223 (circuit stuck high) and P0224 (intermittent), so technicians should check whether any of these appear together, as the combination narrows the diagnosis to a specific wiring or mechanical failure mode.
Common causes
Most-frequently reported root causes when P0222 is logged.
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1
Open circuit (broken wire) in the TPS or APP sensor B-channel signal wire between the sensor and the PCM, causing the voltage to read near 0 V.
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2
B-channel signal wire shorted to a ground line in the harness, clamping the voltage at chassis ground level.
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3
Faulty TPS with a worn or burned-out B-channel resistive track that no longer generates a rising voltage output as the throttle opens.
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4
Faulty APP sensor with internal failure of the B-channel element within the pedal assembly.
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5
Corroded, loose, or unseated connector pin at the throttle body or accelerator pedal position sensor, creating a high-resistance or open connection.
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6
Missing or low 5 V reference voltage from the ECM — without the reference supply, the sensor cannot produce a valid signal voltage.
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7
PCM internal fault misinterpreting the B-channel signal (rare; diagnose only after all external wiring and sensor checks are conclusive).
Symptoms drivers notice
How to diagnose P0222
A typical diagnostic flow when this code is present.
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1
Connect an OBD-II scan tool and retrieve all codes; note any companion codes (P0120, P0220, P0223, P2135) before clearing, as these indicate whether the fault is sensor-only or a wiring/correlation issue.
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2
With the key on and engine off, observe live B-channel voltage on the scan tool while slowly pressing the accelerator pedal — the voltage should sweep upward smoothly from ~0.5 V; a reading stuck near 0 V confirms the low-circuit fault is active.
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3
Verify the ECM is providing the correct 5 V reference voltage at the TPS/APP connector using a digital multimeter; absence of the reference supply will cause both channels to read low.
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4
Inspect the TPS/APP wiring harness visually and with a continuity test — look for bare wires, chafing against brackets, heat damage near the exhaust, and corrosion inside the connector body.
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5
Back-probe the B-channel signal pin and measure resistance from signal pin to chassis ground; near-zero ohms with the sensor disconnected indicates a short to ground in the harness.
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6
Swap in a known-good TPS or APP sensor (or measure A/B voltage curves against spec) to confirm whether the fault is in the sensor or the wiring.
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7
Inspect and clean the throttle body for heavy carbon deposits that could mechanically restrict plate movement and keep the B-channel voltage abnormally low.
Related powertrain codes
- P0120 — Throttle Position Sensor/Switch A Circuit Malfunction
- P0121 — Throttle Position Sensor/Switch A Circuit Range/Performance Problem
- P0122 — Throttle Position Sensor/Switch A Circuit Low Input
- P0123 — Throttle Position Sensor/Switch A Circuit High Input
- P0124 — Throttle Position Sensor/Switch A Circuit Intermittent
- P0220 — Throttle/Pedal Position Sensor/Switch B Circuit Malfunction
Frequently asked questions
Why does a low sensor voltage cause the car to lose power rather than go wide open throttle?
The PCM interprets a stuck-low B-channel reading as a sensor fault, not as a genuine closed-throttle command, because the A-channel (and other data like MAP/MAF) will disagree with a zero-throttle state while the engine is under load. The PCM enters a failsafe mode that limits fuelling as a precaution against acting on a potentially false signal — deliberately sacrificing performance to avoid the risk of uncontrolled acceleration.
Can moisture in the connector cause P0222?
Yes. Water ingress or condensation in the TPS or APP connector can cause oxidation of the signal pins, producing a high-resistance path that drops the B-channel voltage below the 0.5 V threshold. Cleaning the connector with electrical contact cleaner and applying dielectric grease to the pins often resolves moisture-related low-circuit faults.
Does P0222 mean the throttle sensor must be replaced?
Not necessarily. A significant proportion of P0222 faults are caused by wiring and connector issues rather than the sensor itself. Always test the harness continuity and the ECM reference voltage before replacing the sensor, as a broken wire or corroded pin is both cheaper to fix and more common in high-mileage or older vehicles.
How is P0222 different from P0120?
P0120 signals a low-circuit fault on the A-channel of the throttle/pedal position sensor, while P0222 is the same fault on the B-channel. In a dual-redundant electronic throttle system both channels are monitored independently. If only P0222 is present without P0120, the A-channel is functioning correctly and the fault is isolated to the B-channel sensor element or its dedicated wiring.
Disabling P0222 in software
RaceTune can permanently disable P0222 — and any other OBD-II diagnostic trouble code — on every ECU family we support. The monitor is disabled inside the ECU itself, so the fault stops being logged: the warning light stays off and the engine never enters limp mode for this code. The change is tied to your exact software version.
Software modifications affect emissions compliance and are not road-legal in many jurisdictions. RaceTune service files are intended for motorsport, off-road, and export use.
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