how to diagnose a P0301 code in my BMW 5 Series G30/G31 (2017-2024)

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the vehicle is parked on a level surface and the engine is cool.
• Disconnect the negative battery terminal to prevent electrical shock.

2. Inspect and Replace Spark Plug

• Tools Required: Socket set, torque wrench, spark plug socket
• Remove the ignition coil from cylinder 1 by unscrewing the bolts and disconnecting the electrical connector.
• Use the spark plug socket to remove the spark plug from cylinder 1.
• Inspect the old spark plug for wear or fouling; replace if necessary.
• Install the new spark plug, tightening it to the manufacturer's specified torque value (typically around 18 ft-lbs).
• Reattach the ignition coil.

3. Inspect and Replace Ignition Coil

• If the spark plug is in good condition, test the ignition coil.
• Disconnect the ignition coil connector and remove the coil.
• Replace the ignition coil with a new one.
• Reconnect the ignition coil connector securely.

4. Check and Clean Fuel Injector

• If misfire persists, remove the fuel injector for cylinder 1.
• Inspect the injector for clogs or damage. Clean it using an ultrasonic cleaner or replace it if necessary.
• Reinstall the injector, ensuring proper sealing and connection.

5. Perform Compression Test

• If misfire continues, conduct a compression test on cylinder 1.
• Remove the spark plug and insert the compression gauge.
• Crank the engine and note the compression reading. Compare with specifications (typically around 140-200 psi).
• If readings are low, further investigation into the engine's mechanical condition is necessary.