P0118 fault code: Engine Coolant Temperature Circuit High

P0118 means “Engine Coolant Temperature Circuit High” — a fuel and air metering fault in the powertrain.

Can I DIY?

Professional-only boundary. You can confirm the code and compare readings; never open a hot coolant cap.

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 P0118

Do not drive. The engine computer is seeing too high a voltage on the coolant-temperature sensor circuit. That is an electrical reading problem — it does not by itself prove the engine is overheating.

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

  • Engine Coolant Temperature Circuit High: Registration number
  • Engine Coolant Temperature Circuit High: Exact code P0118 and any companion coolant or overheat codes
  • Engine Coolant Temperature Circuit High: Scanner coolant-temperature reading versus the dashboard gauge
  • Engine Coolant Temperature Circuit High: Whether you saw steam, a red temperature warning, or a low cold coolant level
Hot systems

Never open a hot coolant cap — pressure can scald you. Exhaust and catalytic converter get hot enough to burn and ignite debris. Stay clear of electric fans; they can run after shut-off.

P01xxFuel and air metering
MOT fail riskif the warning light stays on

What does P0118 mean?

P0118 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 “Engine Coolant Temperature Circuit High”. The code itself tells you which circuit or system tripped the fault — not always the exact part that failed.

Will P0118 fail an MOT?

An illuminated engine management light is a Major defect at MOT until the fault is repaired and the light stays off. P0118 is a coolant-temperature circuit-high flag, not itself an over-temperature or emissions reading.

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. Car overheating but coolant looks full: stop and recoverNo — do not continue driving while the engine is overheating, even if the expansion bottle looks full. Move only far enough to reach a place of relative safety, switch off, and… Coolant keeps disappearing with no visible leakA falling cold level still means coolant is escaping; never open a hot pressurised system.
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

P0118 — quick answers

Is it safe to drive with P0118?

Do not drive. Driveability guidance is not available for this code — treat as do not drive until checked. If the temperature gauge is already in the hot zone or you see steam, stop and do not open the cap.

Will P0118 fail my MOT?

An illuminated engine management light is a Major defect at MOT until the fault is repaired and the light stays off. P0118 is a coolant-temperature circuit-high flag, not itself an over-temperature or emissions reading.

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.