how to resolve P0301 misfire code on 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 necessary tools and parts.
• Ensure the vehicle is parked on a flat surface and the engine is cool.
• Disconnect the negative battery terminal to prevent electrical shorts.

2. Inspect and Replace Spark Plug

• Tools Required: Socket set, spark plug socket, torque wrench.
• Remove the ignition coil from cylinder 1 by unscrewing the mounting bolts.
• Disconnect the electrical connector from the ignition coil.
• Remove the spark plug using a spark plug socket.
• Inspect the spark plug for signs of fouling or damage. Replace it if necessary.
• Install the new spark plug, torquing it to manufacturer specifications (typically around 15 lb-ft).
• Reconnect the ignition coil and secure it with bolts.

3. Inspect and Replace Ignition Coil

• If the spark plug is in good condition, proceed to inspect the ignition coil.
• Tools Required: Socket set, torque wrench.
• Remove the ignition coil (as described in step 2).
• Test the coil with a multimeter to ensure it is functioning correctly; replace it if it is out of spec.
• Install the new ignition coil, torquing to specifications (usually around 89 lb-in).
• Reconnect the electrical connector.

4. Fuel Injector Inspection

• If the misfire persists, inspect the fuel injector for cylinder 1.
• Tools Required: Noid light or injector tester.
• Disconnect the fuel injector connector and attach the noid light.
• Crank the engine and check if the noid light flashes, indicating the injector is firing.
• If it does not flash, replace the fuel injector.

5. Final Checks

• Reconnect the negative battery terminal.
• Clear the trouble codes using the OBD-II scanner.
• Start the engine and monitor for any reoccurrence of the misfire code.