how to diagnose P0302 code on my BMW 3 Series G20/G21 (2019-2024)

Solution

1. Preparation

• Gather tools: OBD-II scanner, socket set, torque wrench, multimeter, compression tester, and a vacuum gauge.
• Ensure the vehicle is on a level surface and the engine is cool.

2. Replace Spark Plug

1. Remove the engine cover (if applicable) using a socket set.
2. Disconnect the ignition coil connector for cylinder 2.
3. Unscrew the ignition coil using the socket set and remove it from the spark plug.
4. Remove the spark plug using a spark plug socket and inspect it for wear or damage.
5. Install a new spark plug, ensuring it is gapped correctly per manufacturer specifications.
6. Reinstall the ignition coil and reconnect the connector.

3. Replace Ignition Coil (if necessary)

1. If swapping the ignition coil indicated it was faulty, remove the faulty coil as described in the previous step.
2. Install the new ignition coil, ensuring it seats properly.
3. Reconnect the ignition coil connector.

4. Replace Fuel Injector (if necessary)

1. If the fuel injector is faulty, relieve the fuel system pressure before proceeding.
2. Remove the fuel rail (if applicable) by disconnecting the fuel lines and unbolting it from the intake manifold.
3. Replace the injector for cylinder 2 by pulling it out of the rail and installing a new one.
4. Reassemble the fuel rail and reconnect all lines.

5. Perform Compression Test (if necessary)

1. Remove the spark plug from cylinder 2.
2. Insert the compression tester into the spark plug hole.
3. Crank the engine several times to get a reading, and compare it to the manufacturer's specifications.
4. If compression is low, further investigation into mechanical issues is required.