how to resolve P0420 code in my BMW 3 Series G20/G21 (2019-2024)?

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the battery to ensure safety while working on the vehicle.
• Allow the exhaust system to cool down before proceeding.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, ratchet, torque wrench.
• Remove the upstream oxygen sensor using the O2 sensor socket.
• Inspect the sensor for damage; if damaged, replace it with a new one.
• Install the new sensor and torque it to the manufacturer's specification (typically around 30 Nm).
• Repeat the process for the downstream oxygen sensor, if necessary.

3. Inspect or Replace the Catalytic Converter

• Tools Required: Wrench set, jack and jack stands, exhaust pipe cutter (if needed).
• Inspect the catalytic converter for any signs of blockage or physical damage.
• If damage is found or if the catalytic converter is contaminated, remove the old catalytic converter by unbolting it from the exhaust system.
• Install the new catalytic converter and ensure all connections are secure and properly torqued per specifications.

4. Clear Codes and Test Drive

• Reconnect the battery.
• Use the OBD-II scanner to clear the error codes from the vehicle's computer.
• Perform a test drive to ensure the check engine light does not reappear.