Cylinder 5 Misfire Detected
The Powertrain Control Module (PCM) has detected a misfire specifically in cylinder number 5 of the engine. This is typically identified by monitoring variations in the crankshaft rotational speed that occur when a cylinder fails to fire properly.
A misfire can cause raw fuel to enter the exhaust, potentially overheating and destroying the catalytic converter. It should be addressed immediately, especially if the check engine light is flashing.
Common symptoms
- Flashing or illuminated Check Engine Light
- Rough idle or engine shaking
- Noticeable lack of engine power and hesitation during acceleration
- Smell of unburned fuel from the exhaust
- Decreased fuel economy
Likely causes
- Faulty or worn spark plug in cylinder 5
- Defective ignition coil or spark plug wire for cylinder 5
- Clogged or failing fuel injector on cylinder 5
- Vacuum leak affecting cylinder 5
- Low engine compression in cylinder 5 due to internal wear or valve issues
What to check before replacing parts
Read freeze frame data and visually inspect the ignition components for cylinder 5.
Look for: Look for disconnected wires, damaged coil boots, or oil/water in the spark plug well.
Swap the ignition coil from cylinder 5 to another cylinder (e.g., cylinder 1) and clear the codes.
Look for: If the misfire moves to the new cylinder (e.g., P0301), the ignition coil is faulty.
Remove and inspect the spark plug for cylinder 5.
Look for: Check for worn electrodes, carbon fouling, cracked porcelain, or incorrect gap, which indicate a bad spark plug.
Test the fuel injector circuit and operation for cylinder 5 using a noid light or by swapping injectors.
Look for: A lack of pulsing light indicates a circuit issue, while the misfire moving with the injector indicates a clogged or dead injector.
Perform a compression test and cylinder leak-down test on cylinder 5.
Look for: Compression readings significantly lower than other cylinders indicate mechanical issues like burnt valves, worn piston rings, or a blown head gasket.
This page explains the generic P0305 definition and is general reference information, not a diagnosis for your specific vehicle. Actual causes, severity, and repairs vary by make, model, engine, and mileage — always confirm with a scan tool and a qualified technician before replacing parts.
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