my BMW 3 Series E90/E91 has a Check Engine light with code P0301 what should I do

Solution

1. Preparation

• Gather tools and parts needed for the repair.
• Disconnect the battery to ensure safety while working on electrical components.

2. Inspect and Replace Spark Plug

• Remove the engine cover (if applicable) using a socket set.
• Use a spark plug socket to remove the spark plug from cylinder 1.
• Inspect the spark plug for signs of wear, fouling, or damage.
• If necessary, replace the spark plug with a new one, ensuring it matches the specifications (gap, heat range).
• Torque the new spark plug to the manufacturer's specification (typically around 18-22 lb-ft).

3. Check and Replace Ignition Coil

• Disconnect the electrical connector from the ignition coil in cylinder 1.
• Remove the ignition coil using a socket set.
• Inspect the ignition coil for cracks or other damage.
• If the coil is faulty, replace it with a new one and ensure it is seated properly.
• Reconnect the electrical connector securely.

4. Inspect Fuel Injector

• Remove the fuel injector connector from cylinder 1.
• Use a fuel injector cleaning kit to test and clean the injector if clogged.
• If cleaning does not resolve the issue, replace the fuel injector.
• Reconnect the fuel injector connector once done.

5. Compression Test (If Necessary)

• Remove the spark plug from cylinder 1.
• Insert a compression tester into the spark plug hole.
• Crank the engine and take note of the compression reading.
• If the compression is low, further diagnostics are required for potential internal engine problems.