how to fix P0301 misfire 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 necessary tools and parts.
• Disconnect the battery to prevent electrical shorts.
• Ensure the engine is cool before starting any work.

2. Inspect and Replace Spark Plug

• Sub-steps:
  • Remove the engine cover if necessary.
  • Disconnect the ignition coil connector for cylinder 1.
  • Remove the ignition coil using a socket wrench.
  • Remove the spark plug with a spark plug socket.
  • Inspect the spark plug for wear; replace it if necessary (recommended gap: 0.030 inches).
  • Install the new spark plug, ensuring it is torqued to manufacturer specifications (usually around 15 ft-lbs).
  • Reinstall the ignition coil and reconnect the connector.

3. Check and Replace Ignition Coil

• Sub-steps:
  • If the spark plug is in good condition, test the ignition coil using a multimeter (check for resistance according to specifications).
  • If faulty, remove the ignition coil and replace it with a new one.
  • Reconnect the ignition coil connector.

4. Test Fuel Injector

• Sub-steps:
  • Remove the fuel injector connector for cylinder 1.
  • Test the injector resistance with a multimeter (should match specifications).
  • If faulty, replace the fuel injector.
  • Reconnect the fuel injector and ensure it is seated properly.

5. Compression Test

• Sub-steps:
  • Remove the spark plug from cylinder 1.
  • Insert a compression tester into the spark plug hole.
  • Crank the engine and record the compression reading (should be within the manufacturer's range).
  • If compression is low, further investigation is required (valves, piston rings).

6. Inspect for Vacuum Leaks

• Sub-steps:
  • Visually inspect all vacuum lines and connections around the intake manifold.
  • Use a smoke machine or carburetor cleaner to identify leaks.
  • Repair or replace any damaged hoses.