Fault code P0307 – a step-by-step guide to diagnosing and fixing it

Error code P0307 is displayed and the check engine light is on - what does this mean?

The OBD/EOBD system has detected a misfiring fault in cylinder 7. This DTC P0307 trouble code indicates that the seventh cylinder is not firing properly or is misfiring. The fault code mainly occurs in V8 or larger engines, as smaller engines do not have a seventh cylinder.

What can cause this fault code?

• Defective spark plug in cylinder 7
• Damaged ignition coil or ignition cable
• Blocked or defective injection nozzle
• Low compression in the cylinder
• Defective valves or valve timing
• Contaminated or incorrect fuel quality
• Leaking intake manifold gaskets
• Defective crankshaft or camshaft sensor
• Loose or corroded plug connections

What symptoms occur in parallel with error code P0307?

• Engine running unevenly: The engine runs unevenly and jerks, especially when idling
• Loss of power: Noticeable reduction in engine power when accelerating
• Increased fuel consumption: The engine requires more fuel than usual
• Starting problems: The vehicle is harder to start or takes several attempts
• Exhaust odor: Unburned fuel can be smelled in the exhaust gas
• Check engine light: The warning light lights up continuously or flashes
• Catalytic converter damage: Consequential damage can occur with prolonged driving

How can the problem with error code P0307 be rectified?

• The repair should be carried out systematically to identify the exact cause.
• Replace spark plug in cylinder 7: Remove old spark plug, clean thread and install new plug with correct torque
• Check and replace ignition coil and ignition cable: Carry out resistance measurement and replace the defective components if there are deviations
• Clean or replace injection nozzle: Remove the nozzle, have it professionally cleaned or replace it completely if it is very dirty
• Carry out a compression test: Measure compression of all cylinders and repair valves or piston rings if values are low
• Flush fuel system: Replace fuel filter and clean system with additives or professional flushing
• Replace intake manifold gaskets: Locate leaks and replace the corresponding gaskets professionally