my BMW X5 F15 (2014-2019) has a check engine light and code P0301

Solution

1. Preparation

• Gather tools: OBD-II scanner, socket set, torque wrench, multimeter, compression tester, and fuel injector cleaning kit.
• Ensure the engine is cool and the vehicle is in a safe working environment.

2. Replace Spark Plug and Ignition Coil

• Remove Engine Cover (if applicable)
  • Use a socket set to remove bolts securing the engine cover.
• Remove Ignition Coil
  • Disconnect the electrical connector from the ignition coil.
  • Use the socket set to remove the securing bolt and pull out the coil from the cylinder head.
• Replace Spark Plug
  • Use a spark plug socket to remove the spark plug from cylinder 1.
  • Inspect the old spark plug for signs of wear or fouling.
  • Install a new spark plug, ensuring it is gapped correctly to manufacturer specifications (typically around 0.030 inches).
• Reinstall Ignition Coil
  • Insert the new ignition coil into the cylinder head and secure it with the bolt.
  • Reconnect the electrical connector.

3. Inspect and Clean Fuel Injector

• Remove Fuel Injector
  • Relieve fuel system pressure using the fuel pressure relief valve.
  • Disconnect the electrical connector and fuel line from the injector.
  • Remove the securing bolts and pull the injector out.
• Clean or Replace Injector
  • Use a fuel injector cleaning kit to clean the injector or replace it with a new one.
• Reinstall Fuel Injector
  • Ensure O-rings are lubricated and properly positioned, then insert the injector back into place and secure it.

4. Perform Compression Test

• Access Cylinder 1
  • Remove the spark plug from cylinder 1.
• Connect Compression Tester
  • Insert the compression tester into the spark plug hole.
• Crank Engine
  • Crank the engine for several seconds and note the pressure reading; it should be within manufacturer specifications (typically 120-200 psi).
• Evaluate Results
  • If compression is low, further inspection of valves and piston rings may be needed.

5. Check for Vacuum Leaks

• Inspect Hoses
  • Visually inspect vacuum hoses for cracks or disconnections.
• Use Smoke Test
  • If necessary, perform a smoke test to identify any hidden leaks in the intake system.