Bob's Mechanical Repairs

BMW P0301

Bob's Mechanical Repairs — independent family-run garage in Birnam, Dunkeld, Perthshire. Call 01350 727 276 or email [email protected].

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Cylinder 1 misfire on BMW — coils and plugs first, then the well-known injector issues on N20/N54/N55.

BMW P0301 — Cylinder 1 misfire on BMW — coils and plugs first, then the well-known injector issues on N20/N54/N55. Typical UK independent garage cost: £80–£1200.

What actually causes P0301 on a BMW

N54/N55 turbocharged inline-sixes are famous for direct-injection injector failure — they leak or click open at the wrong time, causing single-cylinder misfires. BMW issued an extended warranty on these in the US (8 years/82,000 miles). On N47 diesels P0301 often pairs with swirl flap fragments or injector seal failure.

BMW engines that log P0301

  • N20/N26
  • N54/N55 (335i, 535i, 1M)
  • N47/N57 diesel
  • N52/N53 inline-six

How we diagnose P0301 on a BMW

  1. Swap coil and plug from cyl 1 to cyl 2 — if misfire moves, you've found it
  2. Read injector correction values per cylinder on ISTA or BimmerLink
  3. On N54/N55, check injector index numbers — must match across replacements
  4. On N47 diesel, inspect swirl flaps if not already deleted

The common misdiagnosis to avoid

Replacing plugs and coils on an N54 with a known injector issue is wasted money — get the injectors flow-tested or do a comparative cylinder balance test first.

BMW P0301 repair cost in the UK

Expect £80–£1200 including parts and labour at an independent garage. Main-dealer quotes on BMW are usually higher for the same job, and the spread exists because the cheap cause and the expensive cause throw the same code — pay for the diagnosis before you pay for parts.

Bob's workshop tip

Always use BMW or Bosch OE plugs at the correct heat range — aftermarket NGK / Denso alternatives can run hotter and cause pre-ignition issues on direct-injection BMWs.

Codes usually seen alongside P0301 on BMW

  • P0300
  • P0302
  • P0303
  • P0304
  • P00C6

Symptoms drivers report with P0301

  • Engine 'juddering' like a wet dog when you try to overtake on the A9.
  • The car 'kangaroos' at low speeds, especially when the engine is stone cold.
  • The EML (Engine Management Light) is flashing at you—that's a 'stop now' warning for your catalytic converter.
  • A distinct 'put-put-put' sound from the exhaust pipe at idle.
  • Massive loss of power, feels like you're towing a caravan that isn't there.

Repairs that clear P0301

  • Replace spark plug
  • Swap coil pack
  • Injector test
  • Compression test

For the generic, all-makes explanation of this code — meaning, every known cause and UK cost bands — see our P0301 guide.

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