What Mazda codes (P0011, P0420, P0171, P0299, P0341) actually mean on Mazda engines — the real cause, the common misdiagnosis, and the honest UK repair cost.
These are the OBD fault codes we see most often on Mazda vehicles in the workshop, with the real cause on Mazda engines rather than the generic textbook definition, plus the honest independent-garage cost.
Mazda fault codes explained
- P0011 — Intake cam over-advanced on Mazda Skyactiv-G — the Oil Control Valve and timing chain wear are the usual causes. Typical UK cost £180–£1100.
- P0420 — Catalyst efficiency below threshold on Mazda — Skyactiv-G 2.0/2.5 cat ageing and 4-2-1 manifold cracks. Typical UK cost £400–£1400.
- P0171 — System lean on Mazda — Skyactiv 2.0/2.5 carbon build-up on intake valves and MAF contamination. Typical UK cost £20–£500.
- P0299 — Turbo underboost on Mazda — 2.2 Skyactiv-D and 1.5/2.0 Skyactiv-G turbo pipe splits and actuator wear. Typical UK cost £180–£1600.
- P0341 — Camshaft position sensor performance on Mazda — Skyactiv-G/D CMP sensor and VVT solenoid. Typical UK cost £100–£380.
Codes are generic across manufacturers, but the fix is not. The same code on a Mazda 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.