how to fix 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 ensure safety while working on the vehicle.
• Tools Required: OBD-II scanner, multimeter, infrared thermometer, socket set, torque wrench, safety glasses, gloves.

2. Replace Oxygen Sensors (if faulty)

• Remove the connector from the pre-catalytic and post-catalytic oxygen sensors.
• Use a socket wrench to unscrew the faulty oxygen sensors from the exhaust system.
• Apply anti-seize compound on the threads of the new sensors.
• Install the new oxygen sensors and torque them to the manufacturer's specifications (usually around 30 Nm).
• Reconnect the wiring harness to the sensors.

3. Inspect and Replace Catalytic Converter (if necessary)

• Using a socket set, remove the exhaust bolts securing the catalytic converter to the exhaust manifold and the exhaust pipe.
• Carefully remove the catalytic converter from its location.
• Inspect the old catalytic converter for signs of blockage or damage.
• Install the new catalytic converter and torque the bolts to the specified values (typically 40 Nm).
• Ensure all gaskets are replaced to prevent leaks.

4. Clear Error Codes

• Reconnect the battery.
• Use an OBD-II scanner to clear the P0420 code and any related codes stored in the vehicle's computer.

5. Test Drive

• Take the vehicle for a test drive to allow the onboard diagnostics to re-evaluate the emissions system.
• Monitor the vehicle for any check engine light illumination after the repair.