P0123 fault code: Throttle/Pedal Position Sensor/Switch 'A' Circuit High

P0123 means “Throttle/Pedal Position Sensor/Switch 'A' Circuit High” — a fuel and air metering fault in the powertrain.

Can I DIY?

Professional-only boundary. If the car pulls or idles high, stop; confirm P0123 and do not 'test' the pedal live.

Do not DIYReviewed page boundary
ToolsSpecialist equipment

This is the conservative boundary from the reviewed code record. This page has no frozen site-wide safety grade, so it does not publish a repair route.

What to tell the garage about P0123

Do not drive. Throttle or pedal position sensor A is reporting a high circuit, which can make the engine think the pedal is further down than your foot actually is.

Take these reviewed, code-specific details with you. They help the garage confirm the fault without turning this page into a repair procedure.

  • Throttle/Pedal Position Sensor/Switch 'A' Circuit High: Registration number
  • Throttle/Pedal Position Sensor/Switch 'A' Circuit High: Exact code P0123 and companion throttle or pedal codes
  • Throttle/Pedal Position Sensor/Switch 'A' Circuit High: Whether idle was high, the car crept, or power was missing
  • Throttle/Pedal Position Sensor/Switch 'A' Circuit High: Any reduced-power or limp-mode message
P01xxFuel and air metering
MOT fail riskif the warning light stays on

What does P0123 mean?

P0123 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 High”. The code itself tells you which circuit or system tripped the fault — not always the exact part that failed.

Will P0123 fail an MOT?

An illuminated engine management light is a Major defect at MOT until the fault is repaired and the lamp stays off. P0123 is a high throttle/pedal circuit; dangerous throttle behaviour is also an MOT safety matter.

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.

Related guides

Car diagnostic test cost: compare the scopeUK booking marketplaces currently publish diagnostic averages of about £52–£65. Engine management light on: steady or flashing?A steady engine management light means the computer has stored a fault. Drive with caution and get the code read. A flashing light is different — stop when it is safe.
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

P0123 — quick answers

Is it safe to drive with P0123?

Do not drive. We have no verified driving guidance for P0123 — treat as do not drive until checked. A high throttle/pedal circuit is a drivability and control risk, not a high-idle curiosity.

Will P0123 fail my MOT?

An illuminated engine management light is a Major defect at MOT until the fault is repaired and the lamp stays off. P0123 is a high throttle/pedal circuit; dangerous throttle behaviour is also an MOT safety matter.

Fault-code identifiers are standard diagnostic facts. Their explanations and diagnostic guidance on this site are original editorial summaries, not reproduced SAE wording. MOT defect rules reflect the DVSA MOT inspection manual (2026). This page is general guidance for UK drivers, not a substitute for a professional diagnosis.