my GMC Sierra T1XX (2019-Present) has a check engine light and code P0301

Learn how to diagnose and fix P0301 cylinder 1 misfire in GMC Sierra T1XX. Step-by-step guide with diagnostic procedures and repair instructions.

Solution

1. Preparation

• Gather all necessary tools and parts.
• Disconnect the negative battery terminal to ensure safety.
• Allow the engine to cool before proceeding.

2. Replace Spark Plug

• Tools Required: Socket set, torque wrench, gap gauge.
• Remove the ignition coil from cylinder 1 by unbolting it and disconnecting the electrical connector.
• Remove the spark plug using a spark plug socket.
• Check the spark plug for wear or fouling, and replace it if necessary.
• Gap the new spark plug to the manufacturer’s specification (usually around 0.030-0.035 inches).
• Install the new spark plug and torque it to the manufacturer’s specification (generally around 15-20 lb-ft).
• Reinstall the ignition coil and reconnect the electrical connector.

3. Replace Ignition Coil (if necessary)

• If the ignition coil shows signs of damage or if the spark plug did not resolve the issue, replace the ignition coil.
• Disconnect the electrical connector and remove the coil from its mounting.
• Install the new ignition coil and reconnect the electrical connector.
• Ensure that all connections are secure.

4. Test Fuel Injector (if necessary)

• If issues persist, check the fuel injector for cylinder 1.
• Disconnect the fuel injector connector and remove the injector from the rail.
• Inspect for clogs or leaks and replace if necessary.
• Reinstall the injector, ensuring it is seated properly in the fuel rail and reconnect the electrical connector.

5. Reconnect Battery and Clear Codes

• Reconnect the negative battery terminal.
• Use the OBD-II scanner to clear any stored codes from the ECU.