how to address P0301 code in 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 materials needed:
  • OBD-II scanner
  • Socket set
  • Torque wrench
  • Compression tester
  • Vacuum gauge
  • New spark plug (if needed)
  • New ignition coil (if needed)
  • New fuel injector (if needed)
• Ensure the vehicle is safely parked, with the engine off and cooled down.

2. Inspect and Replace Spark Plug

• Remove the engine cover if applicable.
• Disconnect the ignition coil connector for cylinder 1.
• Remove the ignition coil from cylinder 1.
• Unscrew the spark plug using the appropriate socket.
• Inspect the spark plug; if worn or fouled, replace it with a new one.
• Install the new spark plug to the manufacturer's torque specification (typically 15-20 lb-ft).
• Reinstall the ignition coil and reconnect the connector.

3. Test and Replace Ignition Coil

• If the spark plug replacement did not resolve the issue, inspect the ignition coil.
• Swap the ignition coil from cylinder 1 with another cylinder to see if the misfire code follows the coil.
• If it does, replace the faulty ignition coil with a new one.
• Reconnect the ignition coil connector.

4. Inspect and Replace Fuel Injector

• If the misfire persists, check the fuel injector for cylinder 1.
• Disconnect the fuel injector connector and remove the fuel rail (if necessary, relieve fuel pressure first).
• Inspect the injector for clogs; if defective, replace it with a new one.
• Reinstall the fuel rail and reconnect the injector connector.

5. Perform Compression Test

• If misfire is still present, perform a compression test on cylinder 1.
• Remove the spark plug and insert the compression tester in the spark plug hole.
• Crank the engine and record the compression reading.
• Compare with the manufacturer's specifications (usually 120-200 psi).
• If compression is low, further investigation is needed for potential internal engine problems.

6. Check for Vacuum Leaks

• Use a vacuum gauge to test for leaks or spray carburetor cleaner around the intake manifold and hoses while the engine is running.
• If the engine RPM changes, a vacuum leak is present and should be repaired.