how to fix a misfire on my GMC Sierra T1XX (2019-Present) with 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, basic hand tools.
• Ensure the vehicle is parked on a level surface and the engine is cool.
• Disconnect the negative battery terminal for safety.

2. Replace Spark Plug

1. Remove the ignition coil from cylinder 1 by unscrewing it and disconnecting the electrical connector.
2. Use a spark plug socket to remove the old spark plug from cylinder 1.
3. Inspect the spark plug for signs of wear or damage.
4. Install a new spark plug, ensuring it has the correct gap (refer to the vehicle's specifications).
5. Torque the spark plug to the manufacturer’s specification (usually around 15 lb-ft).

3. Inspect and Replace Ignition Coil

1. After removing the ignition coil in step 2, test it using a multimeter to check for resistance (consult vehicle specifications for correct values).
2. If faulty, replace the ignition coil with a new one.
3. Reconnect the ignition coil and the electrical connector securely.

4. Check and Test Fuel Injector

1. Remove the fuel injector connector for cylinder 1.
2. Use a noid light to check for signal to the injector. If no signal, inspect the wiring.
3. If signal is present, test the injector using a multimeter to measure its resistance (consult specifications).
4. If faulty, replace the fuel injector with a new one.
5. Reconnect the fuel injector connector securely.

5. Perform Compression Test

1. Remove the spark plug from cylinder 1.
2. Insert the compression tester into the spark plug hole.
3. Crank the engine for a few seconds and record the pressure reading.
4. Compare the reading to the manufacturer’s specifications. If low, further mechanical inspection may be required.