BMW Fault Codes — Real Causes, Fixes & UK Costs

What BMW codes (P0171, P0299, P0301, P0420, P2002, P0015) actually mean on BMW engines — the real cause, the common misdiagnosis, and the honest UK repair cost.

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

BMW fault codes explained

• P0171 — System too lean (Bank 1) on BMW — vacuum leaks at the DISA valve, valve cover gasket, or oil filter housing gasket on N42/N43/N46/N52. Typical UK cost £180–£1100.
• P0299 — Turbo underboost on BMW — on N20/N26 it's a cracked charge pipe; on N47/N57 diesels it's the VGT actuator or wastegate sticking. Typical UK cost £50–£1800.
• P0301 — Cylinder 1 misfire on BMW — coils and plugs first, then the well-known injector issues on N20/N54/N55. Typical UK cost £80–£1200.
• P0420 — Catalyst efficiency below threshold on BMW — on N20/N26 it's often a cracked exhaust manifold; on N54/N55 the post-cat O2 sensor is unreliable. Typical UK cost £150–£950.
• P2002 — DPF efficiency below threshold on BMW diesels — the classic N47/N57 'short trip' fault. Almost never the DPF itself first time round. Typical UK cost £220–£1800.
• P0015 — Exhaust camshaft position over-retarded (Bank 1) on BMW — VANOS solenoid is the usual suspect on N20/N52/N55. Typical UK cost £150–£2200.
• P1004 — Valvetronic motor performance — BMW N12/N14/N16 (Mini Cooper too) Valvetronic eccentric shaft sensor or motor failure. Typical UK cost £180–£1600.
• P0401 — EGR flow insufficient on BMW N47/N57 diesels — usually a failed EGR cooler (with a known recall on older N47s) or a clogged intake swirl flap mess. Typical UK cost £220–£950.
• P0203 — Injector circuit Cylinder 3 on BMW — N47/N57 diesels often need an injector replacement plus ISA coding; N20/N55 petrol see solenoid coil failure. Typical UK cost £320–£1100.
• P0106 — MAP sensor / boost sensor range on BMW N20/N55/N47 — Bosch boost pressure sensor in the charge pipe fails, or charge pipe itself cracks. Typical UK cost £140–£580.
• P0562 — System voltage low on BMW — battery registration is mandatory and missing registration is the #1 cause of P0562 on F-series cars. Typical UK cost £140–£580.
• P0100 — MAF circuit malfunction on BMW — N47 diesel MAF failures very common, plus N20/N55 petrol HFM sensor degradation. Typical UK cost £140–£480.
• P0304 — Cylinder 4 misfire on BMW — N47 diesel cyl 4 injector or glow plug; N20/N52/N55 petrol coil pack failure very common. Typical UK cost £120–£580.
• P0128 — Coolant below thermostat regulating temperature on BMW — the electric (map-controlled) thermostat fails in the open position. Typical UK cost £180–£480.
• P0300 — Random misfire on BMW — N20/N26 is coils & valvetronic, N54/N55 is HPFP & injectors, N47 diesel is injectors or swirl flaps. Typical UK cost £140–£1200.
• P244A — DPF differential pressure too low on BMW diesel — N47 and N57 specifically have a known pressure-pipe blockage pattern. Typical UK cost £180–£1800.
• P0016 — Crank/cam correlation on BMW N47 / N57 diesels — the timing chain is at the rear of the engine and notorious for stretching and snapping. Typical UK cost £1400–£3500.
• P0087 — Fuel rail pressure too low on BMW diesel — N47/N57 HPFP failure and rail pressure sensor faults are the common causes. Typical UK cost £260–£4800.
• P0234 — Turbocharger overboost on BMW N20/N55 — wastegate rattle and solenoid faults are the headline causes. Typical UK cost £240–£2800.
• P0011 — Intake VANOS over-advanced on BMW — N42/N46/N52/N54/N55 VANOS solenoids and cam bolts are the usual causes. Typical UK cost £180–£1400.
• P0341 — Camshaft position sensor 'A' range/performance on BMW — sensor failure is common, but on N47/N57 always check chain wear first. Typical UK cost £65–£3200.
• P0455 — EVAP system gross leak on BMW — fuel cap, purge valve and the leak-detection pump (LDP) on US-spec cars. Typical UK cost £40–£320.
• P0017 — Crank to exhaust cam correlation on BMW N47/N57 — the rear-mounted timing chain has stretched, partner code to P0016. Typical UK cost £1400–£3500.
• P0014 — Exhaust cam over-advanced on BMW — VANOS solenoid sludging or, on diesels, chain stretch warning. Typical UK cost £180–£3200.
• P0089 — Fuel pressure regulator performance on BMW — HPFP regulator fault on N20/N54/N55 petrol, CP4 issues on N47/N57 diesel. Typical UK cost £280–£4800.
• P0410 — Secondary air injection on BMW — N52 inline-six SAI pump and check-valve failures. Typical UK cost £260–£1100.
• P0193 — Fuel rail pressure sensor circuit high on BMW — N20/N55 HPFP sensor and N47/N57 diesel rail sensor failures. Typical UK cost £220–£950.
• P0430 — Catalyst efficiency below threshold (Bank 2) on BMW V6/V8 — usually the rear O2 sensor or a sticking VANOS upstream, not a dead cat. Typical UK cost £250–£2400.
• P0335 — Crankshaft position sensor circuit on BMW — heat-soak failure on N47/N57 diesel and N20 petrol. Typical UK cost £55–£220.
• P0302 — Cylinder 2 misfire on BMW — N20/N55/B58 ignition coil or N47 injector flow imbalance. Typical UK cost £90–£850.
• P0090 — Fuel pressure regulator 1 control circuit on BMW — N47/N57 rail pressure regulator (DRV) failure. Typical UK cost £260–£1400.
• P0606 — ECU processor fault on BMW — DDE/DME water ingress on E90/F30 from blocked scuttle drains. Typical UK cost £180–£1200.
• P0507 — Idle speed higher than expected on BMW — vacuum leak from CCV/PCV cracked hoses or DISA flap on N42/N46 and N55. Typical UK cost £90–£320.
• P2463 — DPF soot accumulation on BMW — N47/B47/N57 over-soot, regen failure from short trips. Typical UK cost £180–£2400.
• P0030 — Upstream oxygen sensor heater circuit fault on BMW N-series — DME connector corrosion or sensor heater element failure. Typical UK cost £120–£380.
• P0036 — Post-catalyst sensor heater fault on BMW — sensor ageing on N20/N43, loom damage on N47 diesel. Typical UK cost £130–£400.
• P0402 — EGR flow excessive on BMW diesel — N47/N57 stuck-open valve, often preceded by the well-known EGR cooler recall. Typical UK cost £350–£1200.
• P0130 — Bank 1 sensor 1 circuit fault on BMW — wideband sensor ageing on N20/N43 direct injection. Typical UK cost £140–£420.
• P242F — DPF ash accumulation on BMW N47/N57 diesel — end-of-life DPF, often at 130–160k miles. Typical UK cost £900–£2400.
• P0421 — Warm-up catalyst efficiency below threshold on BMW — N20/N43/N55 manifold-mounted cat failure, often a downstream sensor first. Typical UK cost £350–£1900.

Codes are generic across manufacturers, but the fix is not. The same code on a BMW 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.