how to fix P0301 code on BMW 3 Series G20/G21 (2019-2024)

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 terminal of the battery 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 retaining bolts and disconnecting the electrical connector.
• Remove the spark plug using a spark plug socket and inspect it for signs of wear or damage (e.g., fouling, cracks).
• If needed, replace the spark plug with a new one that meets OEM specifications.
• Install the new spark plug by hand, then torque to the manufacturer’s specifications (typically 22 Nm).

3. Inspect and Replace Ignition Coil

• If the spark plug appears to be in good condition but the misfire persists, proceed to check the ignition coil.
• Tools Required: Socket set
• Remove the ignition coil from cylinder 1 as previously described.
• Test the ignition coil using a multimeter for resistance; if out of specification, replace it with a new coil.
• Reinstall the ignition coil, ensuring it is seated correctly and reconnect the electrical connector.

4. Test Fuel Injector

• If the misfire continues, check the fuel injector for cylinder 1.
• Tools Required: Fuel pressure gauge, injector cleaning kit (if needed)
• Connect the fuel pressure gauge to the fuel rail and check for proper fuel pressure as specified in the service manual.
• If the fuel pressure is low, inspect the fuel filter and pump; replace components as necessary.
• If the injector is clogged, use an injector cleaning kit or replace the injector if cleaning does not resolve the issue.

5. Check for Vacuum Leaks

• Inspect all vacuum lines and the intake manifold for leaks.
• Tools Required: Smoke machine (optional) or soapy water
• If a leak is detected, repair or replace the affected hoses or gaskets to restore proper function.