P0239 fault code: Turbo/Super Charger Boost Sensor 'B' Circuit

Last updated · OBDCode UK editorial

Can I drive with P0239? — Limit driving

Limit driving. Loss of boost-sensor B can confuse sequential or twin-charger control. Stop if power surges, a whistle appears, or the lamp flashes.

P0239 means “Turbo/Super Charger Boost Sensor 'B' Circuit” — a fuel and injector circuits fault in the powertrain. Limit driving. Boost sensor B — a second charger-pressure input on some engines — has a circuit fault, so that extra boost channel is unusable.

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 We do not publish DIY repair or strip-down steps for this code on this page.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.

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.

P02xxFuel and injector circuits
MOT fail riskif the warning light stays on

What does P0239 mean?

P0239 is a generic (SAE standard) powertrain code reported by your car’s engine control unit. It sits in the P02xx block, which covers fuel and injector circuits. The stored description is “Turbo/Super Charger Boost Sensor 'B' Circuit”. The code itself tells you which circuit or system tripped the fault — not always the exact part that failed.

Will P0239 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. The lamp rule applies to sensor B faults the same way as any other MIL.

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.

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.
P0200Injector Circuit/Open P0201Injector Circuit/Open - Cylinder 1 P0202Injector Circuit/Open - Cylinder 2 P0203Injector Circuit/Open - Cylinder 3 P0204Injector Circuit/Open - Cylinder 4 P0205Injector Circuit/Open - Cylinder 5 P0206Injector Circuit/Open - Cylinder 6 P0207Injector Circuit/Open - Cylinder 7

P0239 — quick answers

Is it safe to drive with P0239?

Limit driving. Limit driving. Loss of boost-sensor B can confuse sequential or twin-charger control. Stop if power surges, a whistle appears, or the lamp flashes.

Can I fix P0239 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 P0239 fail my MOT?

An illuminated engine management light is a Major defect at MOT (automatic fail) until the fault is repaired and the light stays off. The lamp rule applies to sensor B faults the same way as any other MIL.

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.