how to troubleshoot P0301 code in my GMC Sierra T1XX (2019-Present)?

Learn how to troubleshoot 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: OBD-II scanner, socket set, torque wrench, multimeter, compression tester, and noid light.
• Ensure the vehicle is parked on a level surface and the engine is cool.

2. Inspect and Replace Spark Plug

• Remove the spark plug from cylinder 1 using a socket and ratchet.
• Inspect the spark plug for signs of wear, fouling, or damage.
• If damaged, replace it with a new spark plug that meets manufacturer specifications (e.g., AC Delco 41-110).
• Torque the new spark plug to the manufacturer's specifications (typically around 15 lb-ft).

3. Check and Replace Ignition Coil

• Disconnect the electrical connector from the ignition coil on cylinder 1.
• Remove the ignition coil using the appropriate socket.
• Inspect for cracks or carbon tracking on the coil.
• Replace with a new ignition coil if necessary, ensuring it is compatible with your vehicle.
• Reinstall the ignition coil and reconnect the electrical connector.

4. Test and Clean Fuel Injector

• Disconnect the fuel injector connector for cylinder 1.
• Use a noid light to check for proper electrical signal; if no signal, investigate wiring issues.
• If the injector is not operating, remove it and clean it using a fuel injector cleaner or replace it if it is defective.
• Reinstall the injector and reconnect the electrical connector.

5. Perform Compression Test

• Remove the spark plug from cylinder 1 and install the compression tester.
• Crank the engine and record the compression reading. Compare it with manufacturer specifications (typically around 130-180 psi).
• If compression is low, further investigation into engine internals may be required.

6. Inspect for Vacuum Leaks

• With the engine running, listen for hissing sounds around the intake manifold and vacuum hoses.
• Use a smoke machine if available to detect leaks.
• Repair any vacuum leaks found by replacing damaged hoses or sealing gaps in the intake manifold.