Fault code P0308 – a step-by-step guide to diagnosing and fixing it

Error code P0308 is displayed and the check engine light is on - what does this mean?

The OBD/EOBD system has registered a misfire detection in cylinder 8. This DTC P0308 indicates incomplete combustion processes or complete misfiring in the eighth cylinder, which can lead to increased emissions and possible catalytic converter damage.

What can cause this fault code?

• Defective spark plug in cylinder 8
• Damaged ignition coil or ignition cable
• Blocked or defective injection nozzle
• Low compression in the cylinder
• Leaking valves or defective valve guides
• Dirty or defective mass air flow sensor
• Defective crankshaft or camshaft sensor
• Clogged fuel filter
• Weak fuel pump
• Loose or corroded plug connections

What symptoms occur in parallel with fault code P0308?

• Engine unsteadiness: Unsteady idling and noticeable vibrations
• Loss of power: Reduced engine power, especially under load
• Increased fuel consumption: Significantly increased fuel consumption
• Starting problems: Difficult starting or longer starting times
• Exhaust odor: Unburned fuel can be smelled in the exhaust gas
• Jerking when accelerating: Uneven power delivery

How can the problem with error code P0308 be rectified?

• The repair requires a systematic diagnosis to identify the exact cause.
• Check and replace spark plug and ignition coil: Remove spark plug in cylinder 8, check for wear and replace if necessary, test ignition coil with multimeter and replace defective component
• Clean or replace injection nozzle: Have injection nozzle professionally cleaned or replace with new nozzle if irreparably damaged
• Carry out a compression test: Measure compression in cylinder 8 and repair valves, piston rings or cylinder head gasket if values are low
• Check the fuel system: Replace fuel filter, test fuel pump and check fuel lines for continuity
• Check sensors and wiring: Check crankshaft and camshaft sensor and all electrical connections for damage and repair