how do I fix P0420 code on BMW 5 Series G30/G31 (2017-2024)?

Solution

1. Preparation

• Gather all necessary tools and parts.
• Disconnect the battery to prevent any electrical issues during the repair.
• Raise the vehicle securely on jack stands.

2. Inspect and Replace Oxygen Sensors

1. Locate the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
2. Remove the electrical connectors from both sensors.
3. Use an O2 sensor socket to unscrew the sensors from the exhaust system.
4. Install the new oxygen sensors in the reverse order of removal, ensuring they are securely tightened to the manufacturer's specifications (usually around 30-40 Nm).
5. Reconnect the electrical connectors.

3. Inspect and Replace Catalytic Converter

1. If the oxygen sensors are functioning correctly, proceed to inspect the catalytic converter.
2. Check for any signs of damage or clogging; replace if necessary.
3. To remove the catalytic converter, unbolt the exhaust flanges using a socket set.
4. Remove any heat shields or brackets that may obstruct access to the catalytic converter.
5. Install the new catalytic converter, ensuring all gaskets and seals are replaced.
6. Torque the bolts to the manufacturer’s specifications.

4. Reassemble and Reset Codes

1. Reattach any heat shields or components removed during the process.
2. Reconnect the battery.
3. Clear the P0420 code using an OBD-II scanner.
4. Start the engine and allow it to reach operating temperature.