P0305 fault code: what it means

P0305: Cylinder 5 is misfiring. Swapping the coil to another cylinder shows whether the coil is the cause.

Engine and gearbox (powertrain) · Costly if missed

Usual causes, most likely first

failed ignition coil on cylinder 5
worn or fouled spark plug
clogged or leaking injector
low compression (valve or ring wear)

P0305 by make

BMW

Cylinder 5 misfire (six-cylinder).

Usual causes: ignition coil; spark plug; fuel injector (DI engines); low compression

Lexus

Cylinder 5 misfire. On IS250/GS300 direct-injection V6 engines single-cylinder misfires at warm idle are a classic sign of intake valve carbon.

Usual causes: carbon build-up on intake valves (walnut blast clean); failing ignition coil; worn spark plug

Mercedes-Benz

Misfire detected in cylinder 5. On Mercedes petrols usually a spark plug or ignition coil on that cylinder.

Usual causes: worn spark plug; failed ignition coil; faulty fuel injector

What the repair usually costs

Petrol fuel injectors (port injection, set)NZ$430–NZ$1,420 · A$400–A$1,360
Coil packs and spark plugs (4-cylinder)NZ$280–NZ$1,000 · A$260–A$920
Coil packs and spark plugs (V6 / V8)NZ$490–NZ$1,780 · A$480–A$1,710
Intake valve carbon clean (walnut blast, direct injection)NZ$530–NZ$1,190 · A$560–A$1,240

Not sure what P0305 means on your car? Ask Credov.

Before you clear it

Write the code down or photograph the scanner first. A code that comes straight back after clearing points to a fault that is still there. A car whose codes were cleared just before you arrived may be hiding one: the scanner's readiness monitors show "not ready" for a while after codes are cleared.

Researched by Credov from manufacturer and workshop sources. A fault code points to where a fault may be; a workshop confirms it with a diagnosis. Browse all fault codes.