Vauxhall Fault Codes — Real Causes, Fixes & UK Costs

What Vauxhall codes (P0299, P0011, P0171, P0420, P0401, P0203) actually mean on Vauxhall engines — the real cause, the common misdiagnosis, and the honest UK repair cost.

These are the OBD fault codes we see most often on Vauxhall vehicles in the workshop, with the real cause on Vauxhall engines rather than the generic textbook definition, plus the honest independent-garage cost.

Vauxhall fault codes explained

• P0299 — Turbo underboost on Vauxhall — almost always a split charge pipe or stretched intercooler clip on Insignia/Astra J 2.0 CDTi. Typical UK cost £50–£1200.
• P0011 — VVT actuator 'A' over-advanced (Bank 1) on Vauxhall — usually the cam phaser or solenoid on the 1.4/1.6/1.8 ecotec engines. Typical UK cost £180–£1200.
• P0171 — System too lean (Bank 1) on Vauxhall — cracked plastic intake manifolds on the 1.4 Turbo A14NET are the single most common cause we see in the workshop, followed by rocker cover PCV failure on the 1.8 Z18XER. Typical UK cost £90–£620.
• P0420 — Catalyst efficiency below threshold on Vauxhall — true cat failure is rare; the usual cause is rear lambda or exhaust leak. Typical UK cost £120–£700.
• P0401 — EGR flow insufficient on Vauxhall 1.7/1.9/2.0 CDTi diesels — sticky EGR valve and crumbling intake manifold flaps on Insignia/Astra/Zafira. Typical UK cost £140–£580.
• P0203 — Injector circuit Cylinder 3 on Vauxhall 1.7/1.9/2.0 CDTi — failing injector or wiring harness fault, particularly on Insignia and Astra J. Typical UK cost £220–£780.
• P0106 — MAP sensor range on Vauxhall 1.4/1.6 turbo and 2.0 CDTi — the cheap GM-spec sensor fails early plus chronic plastic intake leaks on Insignia. Typical UK cost £80–£340.
• P0562 — System voltage low on Vauxhall — Astra J/Insignia alternator failures common, plus battery degradation on stop-start cars. Typical UK cost £140–£480.
• P0100 — MAF circuit malfunction on Vauxhall — 1.9 CDTi and 2.0 CDTi MAF failures very common, plus 1.4 Turbo petrol Astra/Mokka. Typical UK cost £100–£320.
• P0304 — Cylinder 4 misfire on Vauxhall — 1.4/1.6 Turbo coil failure, 1.9/2.0 CDTi injector or glow plug, older 1.6/1.8 plug HT lead issues. Typical UK cost £100–£480.
• P0128 — Coolant below thermostat regulating temperature on Vauxhall — thermostat housing failure is the signature fault. Typical UK cost £100–£260.
• P0300 — Random misfire on Vauxhall — 1.4 Turbo is coils & timing chain, 1.6/1.8 Z-series is usually plugs or coil pack. Typical UK cost £100–£1400.
• P0741 — Torque converter clutch stuck off on Vauxhall auto — Aisin AF40 (6T40/6T45) valve body and ATF condition are usually to blame. Typical UK cost £320–£1400.
• P2463 — DPF soot accumulation on Vauxhall CDTi — Astra, Insignia and Zafira diesels are the worst offenders for failed regens. Typical UK cost £100–£1600.
• P0341 — Camshaft position sensor 'A' range/performance on Vauxhall — sensor failures on Z16/A16 petrol, chain stretch on 1.4T. Typical UK cost £50–£2400.
• P2002 — DPF efficiency below threshold on Vauxhall CDTi — 1.7 CDTi is the worst offender for short-trip-induced substrate damage. Typical UK cost £220–£1800.
• P0234 — Turbocharger overboost on Vauxhall — A14NET 1.4 turbo wastegate solenoid is the headline cause. Typical UK cost £140–£950.
• P0430 — Bank 2 cat efficiency on Vauxhall 2.8 V6 turbo (Insignia VXR / Astra VXR) — manifold cracks and lazy rear O2. Typical UK cost £220–£1800.
• P0500 — Vehicle speed sensor circuit on Vauxhall — ABS wheel speed sensor or front hub failure on Corsa/Astra/Insignia. Typical UK cost £65–£320.
• P0303 — Cylinder 3 misfire on Vauxhall — A14NET coil pack and Z19DTH injector loom chafe. Typical UK cost £70–£500.
• P0016 — Crank/cam correlation Bank 1 on Vauxhall — 1.4 Turbo A14NET and 1.6 SIDI A16XER timing chain stretch. Typical UK cost £550–£1800.
• P0017 — Crank/cam correlation Bank 1 sensor B on Vauxhall — A14NET / A16XER timing chain stretch (sister code to P0016). Typical UK cost £550–£1800.
• P0089 — Fuel pressure regulator on Vauxhall — 1.7/2.0 CDTi rail control valve on Astra/Insignia. Typical UK cost £180–£950.
• P0087 — Fuel rail pressure too low on Vauxhall — 1.7/2.0 CDTi lift pump failure and HP pump wear. Typical UK cost £180–£1600.
• P0193 — Fuel rail pressure sensor high on Vauxhall — 1.7/2.0 CDTi sensor and harness chafe. Typical UK cost £140–£380.
• P0507 — Idle speed higher than expected on Vauxhall — A14NET PCV diaphragm and crankcase pressure issues. Typical UK cost £140–£380.
• P0455 — EVAP gross leak on Vauxhall — fuel cap seal and purge valve on Corsa/Astra. Typical UK cost £20–£220.
• P0410 — Secondary air injection malfunction on Vauxhall — Z18XER/A18XER SAI pump and check valve seizure. Typical UK cost £140–£480.
• P0301 — Cylinder 1 misfire on Vauxhall — A14NET coil pack and Z19DTH injector cyl 1 wear. Typical UK cost £70–£500.
• P0030 — Upstream lambda heater circuit fault on Vauxhall A-series and Z-series engines — connector corrosion is the primary cause. Typical UK cost £60–£240.
• P0036 — Downstream lambda heater fault on Vauxhall — corroded post-cat connector, especially on winter-salted Astras. Typical UK cost £55–£210.
• P0402 — EGR flow excessive on Vauxhall diesel — Z19DTH and A20DTH stuck-open EGR from carbon build-up. Typical UK cost £220–£900.
• P0130 — Upstream O2 circuit fault on Vauxhall — lazy sensor on A14NET and A16XER around 60k miles. Typical UK cost £70–£260.
• P242F — DPF ash saturation on Vauxhall diesel — Z19DTH and A20DTH end-of-life DPFs. Typical UK cost £600–£1800.
• P0421 — Warm-up catalyst efficiency below threshold on Vauxhall — A14NET and A16XER manifold cats, often failed by misfire history. Typical UK cost £200–£1200.

Codes are generic across manufacturers, but the fix is not. The same code on a Vauxhall usually points at a different component than it would on another make, which is why a make-specific diagnosis saves money before any parts are bought.