P0309: Cylinder 9 misfire detected
Flashing light? Stop driving now. Steady light? Drive gently to a mechanic soon.
Can I drive with P0309?
Flashing light? Stop driving now. Steady light? Drive gently to a mechanic soon. If the check engine light is steady, drive gently to a mechanic soon. If the check engine light is FLASHING, stop driving. Unburned fuel can destroy the catalytic converter.
What does P0309 mean?
P0309 stands for Cylinder 9 Misfire Detected.
Symptoms you may notice
- Engine shaking or stumbling under acceleration
- Noticeable power loss and sluggish response
- Flashing or steady check engine light
- Strong fuel odor from the exhaust pipe
How much does it cost to fix?
Repair costs for code P0309 depend on the specific underlying root cause, ranging from simple DIY checks to component replacement. The table below lists the most common causes and rough price ranges in USD:
- Failed ignition coil on cylinder 9
- Fouled spark plug in cylinder 9
- Clogged fuel injector for cylinder 9
- Low compression on valve seat
What to do next
- Observe your check engine light: if it is FLASHING, stop driving now to avoid catalytic converter damage.
- If the check engine light is STEADY, drive gently to a mechanic soon without hard acceleration or towing.
- Inspect the spark plugs, ignition coils, and fuel injector connectors for faults.
Last updated: October 2026
Related codes
General guidance only, not a professional diagnosis. If the check-engine light is flashing, or the car is running rough, overheating or losing power, stop driving and get help.
About this code
Code P0309 occurs on V10 or V12 engines when cylinder 9 misfires. Raw fuel entering the exhaust will cause severe catalytic converter degradation. Follow the flashing light rule immediately.