how to fix P0420 code on my BMW 5 Series G30/G31 (2017-2024)

Solution

1. Preparation

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

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, wrench set, multimeter
• Remove the front oxygen sensor using the O2 sensor socket.
• Inspect the sensor for damage; if faulty, replace it with a new OEM sensor.
• Reinstall the new sensor and reconnect the electrical connector.
• Repeat for the rear oxygen sensor if necessary, following the same steps.

3. Inspect and Replace Catalytic Converter

• Tools Required: Socket set, torque wrench, exhaust hanger removal tool
• Locate the catalytic converter and examine it for any signs of damage or blockage.
• If damaged, unbolt the catalytic converter from the exhaust system.
• Install the new catalytic converter, ensuring proper alignment and secure with bolts.
• Torque the bolts to manufacturer specifications (typically around 30-35 lb-ft, but check the service manual for exact values).
• Reattach any exhaust hangers that were removed.

4. Clear Codes and Test Drive

• Reconnect the battery.
• Use the OBD-II scanner to clear the P0420 code.
• Start the engine and allow it to warm up, then take the vehicle for a test drive to ensure the issue is resolved.