how to diagnose P0301 misfire code on 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 level surface and the engine is cool.
• Disconnect the battery to prevent any electrical issues.

2. Inspect and Replace Spark Plug

• Remove the engine cover, if applicable, to access cylinder 1.
• Use a socket wrench to remove the spark plug from cylinder 1.
• Inspect the spark plug for wear; replace if necessary.
• Install a new spark plug, ensuring it is gapped correctly to manufacturer specifications (typically 0.040 inches for most GM engines).
• Torque the spark plug to the manufacturer's specification (usually around 13 lb-ft).

3. Check and Replace Ignition Coil

• Disconnect the electrical connector from the ignition coil on cylinder 1.
• Remove the ignition coil from its mounting position using a socket wrench.
• Inspect the coil for cracks or signs of damage; replace if needed.
• Install the new ignition coil and reconnect the electrical connector.

4. Inspect and Replace Fuel Injector

• Disconnect the fuel line from the fuel injector (be cautious of fuel spillage).
• Remove the fuel injector connector and unbolt the injector from the intake manifold.
• Inspect the injector for clogs or damage; clean or replace as necessary.
• Install the new or cleaned fuel injector and reconnect the fuel line, ensuring there are no leaks.

5. Perform Compression Test

• Remove the spark plug from cylinder 1 and install a compression gauge.
• Crank the engine a few times and record the compression reading.
• Compare the reading to specifications; if it is low, further diagnosis may be needed for internal engine issues.

6. Reassemble and Test

• Reinstall any components that were removed.
• Reconnect the battery.
• Start the engine and check for new trouble codes.
• Test drive the vehicle to verify the issue is resolved.