P0305 – OBD-II DTC

OBD-II DTC P0305 – Cylinder 4 Misfire Detected

DTC P0305 meaning

DTC P0305 indicates that the Engine Control Module (ECM) has detected a misfire in cylinder number 4. A misfire occurs when the air-fuel mixture in the cylinder fails to ignite properly, leading to a loss of power and increased emissions. This code is part of the On-Board Diagnostics II (OBD-II) system, which monitors the performance of the engine and its components.

DTC P0305 symptoms

Common symptoms associated with DTC P0305 may include:

• Rough idling or engine shaking
• Decreased engine performance
• Increased fuel consumption
• Illuminated Check Engine Light (CEL)
• Engine stalling or hesitation during acceleration

DTC P0305 causes

Several factors can lead to the triggering of DTC P0305, including:

• Faulty spark plug or spark plug wire in cylinder 4
• Defective fuel injector for cylinder 4
• Vacuum leaks affecting cylinder 4
• Low compression in cylinder 4 due to worn piston rings or valves
• Faulty ignition coil for cylinder 4
• Engine control module (ECM) issues

DTC P0305 seriousness

DTC P0305 is considered a serious issue as it can lead to further engine damage if not addressed. Continuous misfiring can cause:

• Increased emissions, leading to potential failure in emissions testing
• Damage to the catalytic converter
• Reduced fuel efficiency
• Overall engine performance degradation

How to diagnose DTC P0305

To diagnose DTC P0305, follow these steps:

1. Use an OBD-II scanner to confirm the presence of the P0305 code.
2. Inspect the spark plug and ignition coil for cylinder 4 for any visible damage.
3. Check the fuel injector operation for cylinder 4.
4. Perform a compression test on cylinder 4 to assess its health.
5. Look for vacuum leaks around the intake manifold and hoses.
6. Review the vehicle’s maintenance history for any recent repairs or changes.

How to fix DTC P0305 step-by-step instructions

To fix DTC P0305, follow these steps:

1. Replace the spark plug and ignition coil for cylinder 4 if they are faulty.
2. Clean or replace the fuel injector for cylinder 4 if it is clogged or malfunctioning.
3. Repair any vacuum leaks found during the diagnosis.
4. Perform a cylinder compression test and address any issues if compression is low.
5. Clear the DTC using an OBD-II scanner and take the vehicle for a test drive to ensure the issue is resolved.

How to erase DTC P0305

To erase DTC P0305, follow these steps:

1. Connect an OBD-II scanner to the vehicle’s diagnostic port.
2. Turn on the ignition without starting the engine.
3. Navigate to the “Erase Codes” or “Clear DTCs” option on the scanner.
4. Confirm the action to clear the codes.
5. Disconnect the scanner and start the engine to verify that the code does not return.

Recommended tools for OBD-II diagnostics

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