BMW misfire fault codes 29CC to 29D2 (cylinders 1 to 6) and P0300 to P0306
The DME has detected a misfire: 29CC is 'misfire, several cylinders', 29CD to 29D2 are cylinders 1 to 6 individually, and P0300 to P0306 are the generic OBD-II equivalents.
What a buyer should take from 29CC
A single-cylinder misfire is most often a £60 coil. The honest seller has already swapped it; the dishonest one has cleared the code before you arrived, so bring a scanner and check for stored and pending misfire codes yourself. Multiple-cylinder misfires (29CC / P0300) on an N54 or N63 with no injector history, or any misfire with low compression, are where the money is.
Symptoms that go with 29CC
- Rough idle, shaking at a standstill, sometimes a flashing engine light
- Hesitation and loss of power under load
- Half-engine (reduced power) light; the DME may shut the injector on the affected cylinder
- Petrol smell from the exhaust, poor economy
- On cold start only: often intake carbon build-up on direct-injection engines
Causes, most likely first
Systems involved: Ignition, fuel injection, intake carbon, compression. Costs are indicative UK independent-specialist figures for 2026; main dealers add 30 to 60 per cent.
| Cause | How likely | Typical UK cost |
|---|---|---|
| Ignition coil failed on that cylinder Swap the coil to another cylinder and see if the code moves | Most common | £40 to £90 per coil, ten minutes |
| Spark plugs worn or wrong heat range Turbo engines want plugs every 30,000 to 40,000 miles | Very common | £100 to £250 for a set fitted |
| Injector failing (N54 piezo, N63, later N55 / B58 solenoid) N54 injectors were a BMW campaign item; replace in matched index batches | Common on N54 / N63 | £200 to £400 per injector fitted |
| Intake valve carbon build-up (any direct-injection engine: N54, N55, N63, S55, early B58) Cold-start misfire that clears when warm | Common past 60,000 miles | £300 to £600 walnut blast |
| Vacuum leak on that cylinder's runner (see 29F1) | Occasional | £100 to £400 |
| Valvetronic or VANOS fault upsetting valve lift / timing (N52, N55) Usually with its own codes | Occasional | £100 to £900 |
| Low compression: burnt valve, broken ring, head gasket, swirl-flap damage on diesels Compression and leak-down test before anything expensive | Least common | £1,500 to £6,000 |
How to diagnose it, cheapest first
- Note which cylinder and whether the misfire is cold-only, idle-only or under load
- Swap the coil (and then the plug) from the flagged cylinder to a neighbour; clear codes; see if the code follows the part
- Inspect plugs for fouling, oil or the wrong type
- On direct-injection engines past 60,000 miles, borescope the intake valves for carbon
- If coils, plugs and injectors are ruled out, compression and leak-down test the cylinder before buying anything else
Buy, negotiate, or walk away
Fine to buy
Single cylinder, coil or plug already replaced with a receipt, smooth idle warm and cold, no pending codes on your own scan.
Negotiate
Cold-start misfire on a direct-injection engine past 60,000 miles (walnut blast, £300 to £600) or an N54 / N63 with one injector code and no injector history.
Walk away
Multiple cylinders misfiring with a flashing engine light, or a compression test the seller refuses, or a diesel misfire with swirl-flap damage suspected.
Seen 29CC on a listing or a scan?
Paste the listing, reg or VIN. Bimmer.AI identifies the exact engine, applies its known failures and costs, and tells you whether this code is a £60 part or a £2,000 conversation on that car.
Run a Bimmer.AI buyer report →Fault-code guidance on this page is general and engine-family based. The same code can have different causes on different engines and years; a proper diagnosis with live data by a BMW specialist is the only way to be sure. Costs are indicative UK ranges that vary by region and parts supply.
Frequently asked questions
What does BMW fault code 29CC mean?
'Misfire, several cylinders': the DME has counted misfires on more than one cylinder, which points at something shared (fuel pressure, a vacuum leak, carbon on the intake valves, a batch of tired plugs) rather than one coil. The individual codes 29CD to 29D2 name cylinders 1 to 6 in order.
Which cylinder is 29D0 on a BMW?
Cylinder 4. The sequence is 29CD cylinder 1, 29CE cylinder 2, 29CF cylinder 3, 29D0 cylinder 4, 29D1 cylinder 5, 29D2 cylinder 6. On BMW straight-sixes cylinder 1 is at the front (radiator end). V8 codes continue in a separate range.
Can a misfire damage my BMW?
A persistent misfire dumps unburnt fuel into the catalytic converter, which can overheat and fail (£800 to £2,000 on most BMWs). A flashing engine warning light means the DME is seeing enough misfires to threaten the cat; stop driving hard and fix it. A steady light with a single-cylinder misfire is less urgent but still a week's job, not a month's.
How much does a BMW ignition coil cost in the UK?
£40 to £90 each for a genuine or Bosch / Delphi / Eldor coil; sets of six run £200 to £400. They pull off with one bolt and take ten minutes each, so most independents charge under half an hour of labour. Plugs at the same time are £100 to £250 for the set.