P0305 on Mazda: How to Diagnose & Fix
Cylinder 5 Misfire Detected
2 Mazda models · 2 documented issues · 1 critical · $50-$300 repair
P0305 on Mazda by model: symptoms, diagnosis and fix
The NB Miata (1999-2005) crankshaft position sensor (CPS) is a known failure point. The sensor deteriorates from engine heat, causing intermittent stalling, no-start conditions, and random misfires. Failure is often heat-related - the car runs fine when cold but stalls or dies after reaching operating temperature.
Common Symptoms
- Engine stalls when hot, restarts after cooling down
- Intermittent no-start condition (cranks but does not fire)
- Random misfires and rough running at operating temperature
- Check engine light with P0335 (CPS circuit) code
How to Fix
Replace crankshaft position sensor with OEM Mazda unit (N3A1-18-221A). Aftermarket sensors (Delphi, Dorman) have higher failure rates on this application. The sensor is located on the rear of the engine block near the flywheel.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Genuine Mazda BP4W-18-221B crankshaft position sensorOEMMazda BP4W-18-221B
Confirm VIN before ordering; thi
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Owner tips & cautions
- TipCarry a spare CPS in the trunk - they fail without warning. Miata.net CPS mega-thread
- TipRoute sensor wiring away from exhaust manifold heat to extend sensor life
Ignition coil-on-plug coils fail causing misfires. Ford 3.0L Duratec V6 coils are prone to cracking and arcing. Usually fails one at a time.
Common Symptoms
- Engine misfire
- Check engine light flashing
- Rough idle
- Loss of power
- Poor fuel economy
How to Fix
Replace failed ignition coil. Replace all 6 spark plugs when replacing any coil. Consider replacing all coils proactively if one fails.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Genuine Mazda AJ09-18-100 direct ignition coilOEMMazda AJ09-18-100
Individual OEM coil replacement after a 3.0L cylinder-specific ignition failure is confirmed Fitment/availability: The inspected direct OEM dealer page identifies AJ09-18-100 and its Tribute fitment through 2001-2010. Confirm VIN/engine …
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P0305 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 P0305 mean on a Mazda?
P0305 stands for "Cylinder 5 Misfire Detected." This code means the engine control module detected a misfire on cylinder number 5, meaning that cylinder is not burning its air-fuel mixture properly on some combustion cycles. The computer senses misfires by watching for tiny fluctuations in crankshaft speed each time a cylinder fails to fire correctly. A misfire wastes fuel, can make the engine run rough or shake, and dumps unburned fuel into the exhaust, which can overheat and damage the catalytic converter. It generally points to a problem with spark, fuel delivery, or compression specifically affecting cylinder 5. On Mazda it is documented across 2 models: MX-5 Miata, Tribute.
What are the most common causes of P0305?
The most common causes of P0305 are: Worn or fouled spark plug on cylinder 5, Failed ignition coil or coil pack for cylinder 5, Faulty or clogged fuel injector on cylinder 5, Vacuum or intake air leak affecting that cylinder, Bad spark plug wire or boot (on applicable engines), Low compression from worn rings, valves, or head gasket, Carbon buildup or sticking valve on cylinder 5, Lean or rich fuel condition affecting the cylinder. The specific cause varies by vehicle.
How much does it cost to fix P0305 on a Mazda?
Published repair estimates on Mazda range from $50 to $300 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.
Looking for P0305 on a different make?
View P0305 across all makes →Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.