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

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the vehicle is on a level surface and the parking brake is engaged.
• Disconnect the battery to prevent electrical shorts.

2. Inspect and Replace Oxygen Sensors

• Sub-steps:
  1. Locate the upstream and downstream oxygen sensors in the exhaust system.
  2. Disconnect the electrical connectors from the oxygen sensors.
  3. Remove the sensors using an oxygen sensor socket or wrench.
  4. Install the new oxygen sensors by threading them into the exhaust and tightening to manufacturer specifications (typically around 30-40 Nm).
  5. Reconnect the electrical connectors.

3. Inspect and Replace the Catalytic Converter (if necessary)

• Sub-steps:
  1. Remove the exhaust components connected to the catalytic converter, if required (may require a socket set).
  2. Unbolt the catalytic converter from the exhaust manifold and the exhaust pipe (use penetrating oil if bolts are rusted).
  3. Remove the catalytic converter from the vehicle.
  4. Install the new catalytic converter, ensuring to align it properly and torque the bolts to manufacturer specifications (typically around 40-50 Nm).
  5. Reinstall any exhaust components removed earlier.

4. Clear Codes and Test Drive

• Sub-steps:
  1. Reconnect the battery.
  2. Use the OBD-II scanner to clear the P0420 code.
  3. Start the engine and allow it to reach operating temperature.
  4. Take the vehicle for a test drive to confirm the repair and monitor for any reoccurrence of the code.