how to fix P0420 code on BMW 3 Series F30/F31 (2012-2019)

Solution

1. Preparation

• Gather tools and parts.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Allow the exhaust system to cool down before starting.

2. Inspect and Replace Oxygen Sensors

1. Remove Oxygen Sensors:

   • Use an O2 sensor socket to carefully remove the upstream and downstream oxygen sensors.
   • Inspect the sensors for contamination or damage.

2. Install New Oxygen Sensors:

   • Apply anti-seize compound on the threads of new sensors.
   • Install the new sensors and torque to manufacturer specifications (usually around 30 Nm).
   • Reconnect the electrical connectors.

3. Inspect and Replace Catalytic Converter (if necessary)

1. Remove Exhaust Components:

   • Use a socket set to remove bolts securing the catalytic converter to the exhaust system.
   • If required, cut the exhaust pipe using a pipe cutter or saw.

2. Install New Catalytic Converter:

   • Position the new catalytic converter in place.
   • Secure with bolts and torque to manufacturer specifications.
   • Reattach any heat shields or additional components removed.

4. Clear Codes and Test

1. Reconnect Battery:

   • Reconnect the negative battery terminal.

2. Clear Error Codes:

   • Use the OBD-II scanner to clear the P0420 code from the vehicle's computer.

3. Test Drive:

   • Perform a test drive to ensure the check engine light does not reappear and monitor vehicle performance.