how to fix P0300 code in GMC Sierra T1XX (2019-Present)

Learn how to diagnose and fix P0300 engine misfire in GMC Sierra T1XX. Step-by-step guide with diagnostic procedures and repair instructions.

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the negative battery terminal to ensure safety while working on electrical components.
• Allow the engine to cool before beginning any work.

2. Inspect and Replace Spark Plugs

• Remove the ignition coil cover if applicable.
• Use a socket wrench to remove the spark plugs.
• Inspect the spark plugs for wear or fouling. Replace if necessary.
• Install new spark plugs, tightening them to the manufacturer’s specified torque (typically around 15-20 lb-ft).
• Reinstall the ignition coil cover.

3. Inspect and Replace Ignition Coils

• Remove the ignition coils by disconnecting the electrical connectors and unscrewing them.
• Inspect for damage. Replace any faulty ignition coils with new ones.
• Reinstall the ignition coils and reconnect the electrical connectors.

4. Check Fuel System

• Connect a fuel pressure gauge to the fuel rail.
• Turn the ignition key to the ON position without starting the engine to check the fuel pressure.
• If the pressure is low, inspect the fuel pump and replace it if necessary.

5. Repair Vacuum Leaks

• Inspect all vacuum hoses and the intake manifold for leaks.
• Replace any damaged hoses and reseal the intake manifold if necessary.

6. Clear Codes and Recheck

• Reconnect the negative battery terminal.
• Use the OBD-II scanner to clear any stored trouble codes.
• Start the engine and monitor for recurring codes.