how to fix P0420 code in BMW 5 Series F10/F11 (2010-2017)

Solution

1. Preparation

• Ensure the vehicle is parked on a level surface.
• Gather all necessary tools and parts.
• Disconnect the negative terminal of the battery to prevent electrical shorts.

2. Inspect and Replace Oxygen Sensors

• Sub-steps:
  1. Locate the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
  2. Disconnect the electrical connectors from both oxygen sensors.
  3. Remove the sensors using an oxygen sensor socket.
  4. Install new oxygen sensors by reversing the removal process; torque to the manufacturer's specifications (usually around 30 Nm or 22 lb-ft).

3. Inspect and Replace the Catalytic Converter

• Sub-steps:
  1. Remove any heat shields or brackets securing the catalytic converter if applicable.
  2. Use a socket set to unbolt the catalytic converter from the exhaust pipes.
  3. Inspect the gasket surfaces and replace gaskets if damaged.
  4. Install the new catalytic converter, ensuring proper alignment; torque bolts to manufacturer specifications.
  5. Reinstall heat shields or brackets as necessary.

4. Clear Codes and Test

• Sub-steps:
  1. Reconnect the negative battery terminal.
  2. Use an OBD-II scanner to clear the P0420 code.
  3. Start the engine and let it reach operating temperature.
  4. Take the vehicle for a test drive to monitor for reoccurrence of the check engine light.