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

Solution

1. Preparation

• Gather tools and parts required for the repair.
• Disconnect the battery to prevent electrical shorts.
• Raise the vehicle using a jack and secure it with jack stands.

2. Inspect and Replace Oxygen Sensors

1. Locate the upstream (pre-catalytic converter) and downstream (post-catalytic converter) oxygen sensors.
2. Use an O2 sensor socket to remove the upstream oxygen sensor.
3. Inspect the sensor for contamination or damage; replace if necessary.
4. Repeat the process for the downstream oxygen sensor.
5. Install new oxygen sensors, ensuring proper torque (typically 30 Nm).

3. Inspect and Clean Catalytic Converter

1. Remove the catalytic converter from the exhaust system by loosening the clamps or bolts with a socket set.
2. Inspect the converter for any signs of damage or blockage.
3. If the converter is clogged but not physically damaged, use a catalytic converter cleaner according to product instructions.
4. Reinstall the catalytic converter, ensuring all bolts are torqued to specification (usually 40 Nm).

4. Clear Codes and Test Drive

1. Reconnect the battery.
2. Use the OBD-II scanner to clear the P0420 code from the vehicle's computer.
3. Test drive the vehicle under various conditions to ensure the issue is resolved.