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

Solution

1. Preparation

• Tools Required: OBD-II scanner, multimeter, infrared thermometer, socket set, jack stands, safety goggles, gloves.
• Ensure the vehicle is parked on a flat surface and the engine is cool. Disconnect the battery before starting any work.

2. Inspect and Replace Oxygen Sensors

1. Locate the oxygen sensors: Identify the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
2. Disconnect the wiring connectors: Carefully unplug the connectors from each sensor.
3. Remove the sensors: Use a socket or wrench to unscrew the sensors from the exhaust system.
4. Install new sensors: Apply anti-seize compound to the threads of the new oxygen sensors. Install and torque them to the manufacturer’s specifications (typically 30 Nm).
5. Reconnect wiring: Plug the connectors back into the new sensors.

3. Replace Catalytic Converter (if necessary)

1. Raise the vehicle: Use jack stands to securely lift the vehicle.
2. Remove exhaust components: Loosen and remove any bolts or clamps securing the catalytic converter to the exhaust system.
3. Disconnect the catalytic converter: Carefully slide the converter out of the exhaust pipe.
4. Install new catalytic converter: Position the new catalytic converter in place and secure it with bolts or clamps, ensuring a tight fit.
5. Reattach any exhaust components: Reinstall any parts that were removed, ensuring all connections are tight and leak-free.

4. Clear Error Codes

1. Reconnect the battery: Ensure all connections are secure and then reconnect the battery.
2. Use the OBD-II scanner: Clear the P0420 code from the vehicle's computer and check for any pending codes.