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

Solution

1. Preparation

• Gather tools and parts.
• Ensure the vehicle is parked on a level surface and the engine is cool.
• Disconnect the battery to prevent any electrical shorts during the repair.

2. Inspect and Replace Oxygen Sensors

• Sub-steps:
  1. Locate the upstream and downstream oxygen sensors in the exhaust system.
  2. Using an O2 sensor socket, carefully remove the sensors.
  3. Install the new sensors, ensuring they are tightened to the manufacturer's torque specifications (typically around 30 Nm).
  4. Reconnect the electrical connectors for the sensors.

3. Examine the Catalytic Converter

• Sub-steps:
  1. Visually inspect the catalytic converter for any physical damage or signs of overheating (e.g., discoloration).
  2. If damaged, remove the exhaust pipe sections leading to the catalytic converter using a socket set.
  3. Replace the catalytic converter with a new, OEM-approved unit, ensuring proper alignment and secure fastening.
  4. Reconnect any exhaust brackets and tighten them to the specified torque.

4. Clear Error Codes

• Sub-steps:
  1. Reconnect the battery.
  2. Use the OBD-II scanner to clear any existing P0420 and related error codes.
  3. Start the engine and allow it to reach operating temperature.