Also known as: n54b30, 3.0 twin-turbo straight-six, 335i engine, 535i engine, n54b30o0, n54b30t0
BMW's first mass-produced turbocharged petrol engine of the modern era, and the one that taught a generation of owners what direct injection costs. Two small low-pressure turbochargers rather than one large unit — the arrangement BMW marketed as TwinPower Turbo before the name migrated to single twin-scroll engines, which is why the badge is not a reliable guide to what is under the bonnet.
The diagnostic history is dominated by the high-pressure fuel supply: pump failures and injector faults were common enough on early cars to become the canonical case of expensive misdiagnosis, because a failing pump and a failing injector produce overlapping fuelling and misfire codes. Read fuel-rail pressure against commanded pressure before condemning either.
Carbon accumulation on the intake valves is structural rather than a fault — port injection washes valves and direct injection does not — so a running complaint at high mileage on an engine with no stored codes is worth walking through before the fuel system.
Cars fitted with this engine
6 generations, across 1 make. From the authored catalogue — an absent car means the catalogue has not reached it, not that the engine was never fitted.
Information, not instruction
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Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Posted about this engine
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What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
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