P0308 on BMW: How to Diagnose & Fix
Cylinder 8 Misfire Detected
1 BMW model · 1 documented issue · $180-$1,200 repair
P0308 on BMW by model: symptoms, diagnosis and fix
Ignition coils on S63TU and S63B44T4 engines (F10 M5 2013-2016, F90 M5 2018-2023) fail far more frequently than on other BMW engines, with failures common before 30,000 miles. High-performance turbocharged nature of S63 creates extreme heat and electrical demands that stress ignition coils beyond their design limits. When one coil fails, it typically signals that other coils are nearing end of life. Failed coils cause misfires, rough running, and can damage catalytic converters if not addressed promptly. Owners on M5Board report that coil failure before 30,000 miles is common on S63 engines, so it is worth budgeting for. When one coil fails, M5Post members recommend replacing all 8 at once, since owners report the rest often fail within about 10,000 miles; this saves a second service visit and its labor cost.
Common Symptoms
- Engine misfires, especially under load or acceleration
- Rough idle and unstable engine operation
- Check engine light with misfire codes (P0300-P0308)
- Reduced power output
- Poor fuel economy
- Potential catalytic converter damage from unburned fuel
How to Fix
Replace failed ignition coil(s) immediately to prevent catalytic converter damage ($3,000-$5,000 additional). When one coil fails, M5Post recommends replacing all 8 coils as preventative maintenance ($600-$900 parts + labor) - they typically fail within a similar timeframe, and this saves a second service visit. Use OEM Bosch coils for best reliability ($50-$80 each) - aftermarket options fail even faster on S63 due to heat and electrical demands. Replace spark plugs simultaneously if mileage exceeds 30,000 miles ($280-$320 for 8 plugs). Labor: 1-2 hours. Single coil replacement: $179-$235.
Sources for this issue (1)
- BMW Ignition Coils for BMW 5 Series F10 (Turner Motorsport)parts-reference
P0308 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P0308 mean on a BMW?
P0308 stands for "Cylinder 8 Misfire Detected." P0308 means the engine computer detected a misfire on cylinder number 8 — that cylinder is failing to combust properly or at the correct time. The PCM identifies it by monitoring crankshaft speed variations as cylinder 8 fires. Misfires waste fuel, increase emissions, and can overheat and damage the catalytic converter, so a hard misfire may cause a flashing check engine light. Typical symptoms include rough idle, vibration, hesitation, and reduced power. On BMW it is documented across 1 model: M5.
What are the most common causes of P0308?
The most common causes of P0308 are: Worn, fouled, or incorrectly gapped spark plug on cylinder 8, Failed ignition coil or coil-on-plug for cylinder 8, Faulty, clogged, or leaking fuel injector, Vacuum or intake air leak affecting that cylinder, Low compression (worn rings, burnt/leaking valve, head gasket), Damaged spark plug wire or boot (on applicable engines), Carbon buildup or sticking valve. The specific cause varies by vehicle.
How much does it cost to fix P0308 on a BMW?
Published repair estimates on BMW range from $180 to $1,200 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
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Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.