P0122 fault code: Throttle/Pedal Position Sensor/Switch 'A' Circuit Low

Last updated 19 August 2026 · OBDCode UK editorial

Can I drive with P0122? — Drive with care

A throttle-position circuit fault on its own does not normally mean you must stop driving while the car still follows the pedal, and it is not a clean bill of health. Stop at once if response goes dead, the engine surges, or you cannot control engine speed.

P0122 means “Throttle/Pedal Position Sensor/Switch 'A' Circuit Low” — a fuel and air metering fault in the powertrain. Drive with care. The engine computer is seeing too low a voltage from the main throttle or accelerator-pedal position sensor (circuit A), so it cannot trust how far the pedal or throttle is open.

Can I DIY?

Caution — conditions apply. We do not publish DIY repair or strip-down steps for this code on this page. Read codes and observe only; leave the repair to a qualified garage.

Caution — conditions applyDIY boundary

ToolsBasic tools only — for example a household socket set, tyre gauge, or a consumer OBD reader.

Some checks may be possible for a careful DIY driver with the right tools and a safe place to work. Stop if anything feels beyond your skill or kit.

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Fault code: P0122 — Throttle/Pedal Position Sensor/Switch 'A' Circuit Low.
Can I drive: Drive with care. A throttle-position circuit fault on its own does not normally mean you must stop driving while the car still follows the pedal, and it is not a clean bill of health. Stop at once if response goes dead, the engine surges, or you cannot control engine speed.
Question: What does this code mean for a UK car, is it safe to drive, what are the most likely causes, and what should I ask a garage to check before replacing parts?

For your garage

REPAIR BRIEF — prepared by the owner with obdcode.co.uk
Fault code: P0122 — Throttle/Pedal Position Sensor/Switch 'A' Circuit Low.
Drive guidance from obdcode.co.uk: Drive with care. A throttle-position circuit fault on its own does not normally mean you must stop driving while the car still follows the pedal, and it is not a clean bill of health. Stop at once if response goes dead, the engine surges, or you cannot control engine speed.
Owner’s request: please diagnose before replacing parts, itemise diagnosis time separately, and quote before any work beyond diagnosis.

P01xxFuel and air metering

MOT fail riskif the warning light stays on

What does P0122 mean?

P0122 is a generic (SAE standard) powertrain code reported by your car’s engine control unit. It sits in the P01xx block, which covers fuel and air metering. The stored description is “Throttle/Pedal Position Sensor/Switch 'A' Circuit Low”. The code itself tells you which circuit or system tripped the fault — not always the exact part that failed.

How to diagnose P0122 yourself

Confirm P0122 and freeze-frame: With the car stationary in open air, scan the OBD-II port. Note whether P0122 is current or pending, freeze-frame pedal or throttle position if shown, and any other throttle or pedal circuit codes. Stop if: The engine management light is flashing, or the engine will not idle in a controlled way while you scan.

Park safely and switch off before locating the socket. Its position varies, so use the vehicle handbook and never force or dismantle trim.
Note pedal versus engine response: From the driver’s seat on firm level ground, with space ahead clear, press the accelerator gently and watch whether engine speed rises smoothly. Do not remove the air intake, throttle body, or any connector. Stop if: Engine speed does not follow the pedal, the car surges, or you cannot keep a safe idle.

Will P0122 fail an MOT?

An illuminated engine management light is a Major defect at MOT (automatic fail) until the fault is repaired and the light stays off.

Before booking your test, check what usually fails on your car: see our MOT pass rates by make and model, built from 33.1 million DVSA tests.

What the MOT data says

No MOT certificate item corresponds to this code; MOT outcome data cannot be shown.

P0100Mass or Volume Air Flow Circuit P0101Mass or Volume Air Flow Circuit Range/Performance P0102Mass or Volume Air Flow Circuit Low Input P0103Mass or Volume Air Flow Circuit High Input P0104Mass or Volume Air Flow Circuit Intermittent P0105Manifold Absolute Pressure/Barometric Pressure Circuit P0106Manifold Absolute Pressure/Barometric Pressure Circuit Range/Performance P0107Manifold Absolute Pressure/Barometric Pressure Circuit Low Input

P0122 — quick answers

Is it safe to drive with P0122?

Drive with care. A throttle-position circuit fault on its own does not normally mean you must stop driving while the car still follows the pedal, and it is not a clean bill of health. Stop at once if response goes dead, the engine surges, or you cannot control engine speed.

Can I fix P0122 myself?

Caution — conditions apply. We do not publish DIY repair or strip-down steps for this code on this page. Read codes and observe only; leave the repair to a qualified garage. Basic tools only — for example a household socket set, tyre gauge, or a consumer OBD reader.

Will P0122 fail my MOT?