P0305

What it means

P0305 means the engine control unit has detected a misfire on cylinder 5 using crankshaft speed variations. The misfire was seen often enough, or severely enough, over a set number of engine cycles to set the code. The code only applies to engines with at least five cylinders, and the cylinder numbering and firing order depend on the engine.

Symptoms

• Rough idle or engine shaking
• Flashing or steady engine warning light
• Loss of power or hesitation under acceleration
• Hard starting or stalling
• Smell of unburnt fuel from the exhaust
• Increased fuel consumption

Possible causes

• Worn, fouled or incorrectly gapped spark plug on cylinder 5likely
• Faulty ignition coil or coil connector on cylinder 5likely
• Faulty or blocked fuel injector on cylinder 5, or a wiring fault to itpossible
• Vacuum or intake leak affecting cylinder 5, such as a cracked intake hose or leaking manifold gasketpossible
• Low compression on cylinder 5 from valve, piston ring or head gasket problemspossible
• Wiring or connector fault in the ignition or injector circuitpossible
• Fuel supply or pressure problem, or engine control unit faultrare

How to diagnose

1. Read all stored codes and freeze frame data to see load, speed and temperature when the misfire occurred, and check for other misfire or fuel trim codes.
2. Check live misfire counters to confirm the misfire is on cylinder 5 only and whether it happens at idle, under load or when cold.
3. Identify cylinder 5 for this engine from the workshop data, then inspect its coil, connector, wiring and spark plug for damage, oil, moisture or wear.
4. Swap the cylinder 5 coil with another cylinder and see whether the misfire follows the coil, repeating with the spark plug if needed.
5. Check for intake leaks and inspect hoses and manifold gaskets, and review fuel trim data for signs of a lean condition.
6. Test the cylinder 5 injector for resistance, driver signal and correct operation, and check its connector.
7. Carry out a compression or cylinder leak-down test on cylinder 5 if ignition and fuel checks are fine.
8. Check fuel pressure against the manufacturer's specification for the engine.

How to fix

• Replace the spark plugs, as a set where appropriate, with the correct type and gap for the engine.
• Replace the faulty ignition coil on cylinder 5.
• Clean or replace the faulty fuel injector, or repair its wiring or connector.
• Repair any intake or vacuum leaks found.
• Repair the mechanical fault causing low compression, which depends on the findings of the engine tests.
• Repair damaged wiring or connectors in the affected circuit.

Can I keep driving?

Nearby codes

• P0304GenericCylinder 4 Misfire Detected
• P0306GenericCylinder 6 Misfire Detected