how to troubleshoot the P0301 misfire code in my GMC Sierra T1XX (2019-Present)

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 tools and parts needed for the repair.
• Disconnect the battery to ensure safety while working on electrical systems.

2. Inspect and Replace Spark Plug

• Sub-steps:
  1. Remove the ignition coil from cylinder 1.
  2. Remove the spark plug using a spark plug socket and ratchet.
  3. Inspect the spark plug for signs of wear or damage (e.g., excessive carbon buildup, cracks).
  4. If necessary, replace the spark plug with a new one that meets OEM specifications (e.g., gap size).
  5. Reinstall the spark plug and ignition coil.

3. Check and Replace Ignition Coil

• Sub-steps:
  1. If the spark plug is in good condition, test the ignition coil using a multimeter for resistance.
  2. If the coil is faulty, remove it and replace it with a new one designed for the vehicle.
  3. Reconnect the ignition coil to the spark plug.

4. Fuel System Inspection

• Sub-steps:
  1. Connect a fuel pressure gauge to the fuel rail.
  2. Turn the ignition to the ON position (do not start) and check the fuel pressure against manufacturer specifications.
  3. If the fuel pressure is low, inspect the fuel pump and fuel filter for issues and replace if necessary.

5. Vacuum Leak Check

• Sub-steps:
  1. Start the engine and use a smoke machine or carburetor cleaner to check for vacuum leaks around intake manifold gaskets and hoses.
  2. Repair or replace any leaking components found.