why does my GMC Sierra T1XX (2019-Present) have a check engine light and code P0301?

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

• Tools Required: OBD-II scanner, socket set, torque wrench, compression tester, multimeter, noid light.
• Clear the error codes using the OBD-II scanner.
• Ensure the engine is cool and the vehicle is on a stable surface.

2. Inspect and Replace Ignition Components

• Sub-steps:
  1. Remove the engine cover (if applicable) using a socket set.
  2. Disconnect the electrical connector from the ignition coil on cylinder 1.
  3. Remove the ignition coil by unscrewing the mounting bolts.
  4. Inspect the spark plug for wear or damage; replace if necessary.
  5. Install the new spark plug using a torque wrench (typically to 15-20 lb-ft).
  6. Reinstall the ignition coil and reconnect the electrical connector.

3. Inspect Fuel Injector

• Sub-steps:
  1. Disconnect the fuel injector connector on cylinder 1.
  2. Using a noid light, check for proper signal to the injector while cranking the engine.
  3. If no signal is present, check the wiring harness for continuity and repair if necessary.
  4. If the injector is faulty, remove it and replace it with a new one.

4. Perform Compression Test

• Sub-steps:
  1. Remove the spark plug from cylinder 1.
  2. Insert the compression tester into the spark plug hole.
  3. Crank the engine for about 5 seconds and record the maximum pressure reading.
  4. Compare the reading to specifications (usually 120-200 psi) and assess for engine health.

5. Check for Vacuum Leaks

• Sub-steps:
  1. Visually inspect all vacuum hoses connected to the intake manifold.
  2. Use a smoke machine or carburetor cleaner to detect leaks while the engine is running.
  3. Repair or replace any leaking hoses or gaskets as necessary.