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

Solution

1. Preparation

• Gather tools and parts needed for the repair.
• Disconnect the battery to prevent any electrical shorts during the repair process.
• Ensure the vehicle is on a level surface and secured with jack stands if working underneath.

2. Inspect and Replace Oxygen Sensors

1. Locate Oxygen Sensors: Identify the locations of the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
2. Remove Old Sensors: Using an oxygen sensor socket, disconnect the electrical connector and remove the sensors from the exhaust system.
3. Install New Sensors: Apply anti-seize compound on the threads of the new sensors and install them in reverse order. Tighten to manufacturer specifications (usually around 30 ft-lbs).
4. Reconnect Electrical Connectors: Ensure that the sensors are properly connected.

3. Inspect and Replace Catalytic Converter (if necessary)

1. Remove Exhaust Components: If necessary, unbolt and remove the exhaust components leading to the catalytic converter.
2. Remove Catalytic Converter: Use a socket set to unbolt the catalytic converter from the exhaust manifold and the downstream pipe.
3. Install New Catalytic Converter: Position the new catalytic converter in place and secure it using new gaskets and bolts to the manufacturer's torque specifications.
4. Reassemble Exhaust Components: Reattach any exhaust components removed during the process.

4. Clear Error Codes

• Reconnect the battery and use the OBD-II scanner to clear the P0420 code from the vehicle's computer.

5. Test Drive

• Conduct a test drive for at least 20 minutes to allow the vehicle to enter closed-loop operation and monitor for any check engine light reactivation.