P0305
Cylinder 5 Misfire Detected
If your code reader dashboard displays the generic DTC error code P0305, your vehicle is currently experiencing an active failure related to "Cylinder 5 Misfire Detected". Proper system troubleshooting is required to safely clear this warning.
Driver's Summary
Storing code P0305 is your car's way of telling you something is wrong with the cylinder 5 misfire detected. Typical symptoms include engine shaking, flashing check engine light, lack of power. This is a serious fault — avoid extended driving and have your vehicle inspected by a mechanic as soon as possible to prevent further damage.
Symptoms
Engine shaking, flashing check engine light, lack of power
Common Causes
- Fouled spark plug in cylinder 5
- Failed ignition coil pack
- Clogged fuel injector
- Low compression in cylinder 5
How to Fix
- 1 Replace spark plug
- 2 Swap ignition coil to test, replace if needed
- 3 Perform fuel injector flush or replacement
- 4 Run a compression test
Technical Explanation
Code P0305 is confirmed when the ECM's diagnostic algorithm detects a parameter deviation that persists across a defined number of consecutive drive cycles. For injector-specific codes, the ECM monitors the injector control circuit voltage drop during each pulse; a shorted or open injector presents a characteristic resistance signature that differs measurably from a healthy unit. The MIL illuminates after the fault is confirmed on two consecutive drive cycles, and the freeze frame data captured at first detection is stored in the PCM's memory for diagnostic reference.
Is It Safe to Drive?
Driving with an active P0305 fault risks accelerating damage to fouled spark plug in cylinder 5 and related components. The longer the fault persists, the more expensive the eventual repair becomes — what starts as a sensor or solenoid issue can escalate to major mechanical failure.
Mechanic's Pro Tip
The fastest isolation technique for P0305 is the coil swap test: move the ignition coil from the affected cylinder to a neighboring cylinder and clear the code. If the misfire follows the coil, it's the coil. If it stays on the same cylinder, focus on the spark plug, injector, or compression. Never replace coils without also replacing the spark plug in that cylinder — a fouled plug will kill a new coil within weeks.
Spark plug/coil: $100 - $250; Injector: $200 - $600