what causes the P0303 code in my BMW 5 Series F10/F11 (2010-2017) and how to resolve it

Solution

1. Preparation

• Gather tools such as an OBD-II scanner, multimeter, compression tester, socket set, and torque wrench.
• Ensure the vehicle is on a flat surface, and the engine is cool before starting work.

2. Replace Ignition Coil and Spark Plug

1. Disconnect the battery: Remove the negative terminal to ensure safety.
2. Remove engine cover: Use the socket set to take off any fasteners holding the cover in place.
3. Remove ignition coil: Unplug the electrical connector, then remove the bolt securing the coil and take it out.
4. Remove spark plug: Use a spark plug socket to carefully unscrew the spark plug from cylinder 3.
5. Install new spark plug: Ensure it is gapped correctly (typically 0.032-0.036 inches) and torque it to the manufacturer’s specification (usually around 18-22 lb-ft).
6. Install new ignition coil: Secure it in place and reconnect the electrical connector.

3. Test and Replace Fuel Injector (if needed)

1. Check injector resistance: Use a multimeter to measure resistance across the fuel injector connectors; compare it to the specifications for your model.
2. Confirm fuel delivery: If the resistance is within spec, perform a fuel pressure test to ensure proper fuel delivery to cylinder 3.
3. Replace injector: If faulty, disconnect the fuel line, remove the injector from its seat, and install a new one, ensuring proper sealing.

4. Address Compression Issues (if applicable)

1. Perform a compression test: Follow the manufacturer's procedures to ensure cylinder 3 has adequate compression (typically 120 psi or higher).
2. Inspect for mechanical damage: If compression is low, further inspection of the valves, piston, or head gasket may be necessary.