how to fix the P0301 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 equipment: OBD-II scanner, socket set, torque wrench, compression tester, multimeter, fuel injector cleaner, and shop manual.
• Ensure the vehicle is parked on a level surface and the engine is cool.

2. Inspect and Replace Spark Plug and Ignition Coil

• Remove the engine cover (if applicable) using a socket set.
• Disconnect the ignition coil connector for cylinder 1.
• Remove the ignition coil by unscrewing the bolts and gently pulling it out.
• Remove the spark plug using a spark plug socket. Inspect for damage or excessive wear.
• If necessary, replace the spark plug with one that meets OEM specifications (typically NGK or AC Delco).
• Install the new spark plug to the manufacturer’s torque specification (usually around 15-20 lb-ft).
• Reinstall the ignition coil and reconnect the connector, ensuring it clicks into place.

3. Check and Clean or Replace Fuel Injector

• Remove the fuel rail if necessary (check service manual for specific instructions).
• Disconnect the fuel injector connector for cylinder 1.
• Using a multimeter, test the injector for resistance (specifications typically around 12-16 ohms).
• If the injector is faulty, replace it with a new one that matches OEM specifications.
• If cleaning, use a fuel injector cleaner and follow the instructions on the product.
• Reassemble the fuel rail and reconnect all connectors.

4. Perform Compression Test

• Remove the spark plug from cylinder 1.
• Insert the compression tester into the spark plug hole.
• Crank the engine for a few seconds, then record the compression reading.
• Compare the reading to the manufacturer's specifications (usually around 120-180 psi).
• If compression is low, further investigation may be needed for internal engine issues.

5. Inspect for Vacuum Leaks

• Visually inspect vacuum hoses and the intake manifold for any cracks or loose connections.
• Use a smoke machine or carburetor cleaner to check for leaks around the intake manifold.
• Repair or replace any damaged hoses or gaskets as needed.