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

Solution

1. Preparation

• Gather all necessary tools and parts.
• Disconnect the battery to ensure safety.
• Lift the vehicle using a jack and secure it on jack stands.

2. Inspect and Clean

• Inspect Exhaust System:
  • Check for any leaks or cracks in the exhaust pipes and connections.
  • Repair any leaks found using exhaust sealant or replace damaged sections.
• Clean O2 Sensors:
  • Carefully remove the upstream and downstream oxygen sensors using an O2 sensor socket.
  • Clean the threads and sensor tip with a suitable cleaner. Avoid harsh cleaners that may damage the sensor.

3. Replace Catalytic Converter (if necessary)

• Remove Old Catalytic Converter:
  • Use a socket set to unbolt the catalytic converter from the exhaust system.
  • Disconnect any sensors or heat shields attached to the converter.
• Install New Catalytic Converter:
  • Position the new catalytic converter in place, ensuring proper alignment.
  • Torque the bolts to the manufacturer's specifications (usually around 25-35 lb-ft, but check service manual).

4. Reinstall O2 Sensors

• Reinstall the cleaned or new O2 sensors, ensuring they are properly seated and torqued to specifications (typically 30 lb-ft).

5. Final Checks

• Reconnect the battery.
• Start the engine and allow it to reach operating temperature.
• Check for any exhaust leaks and ensure the engine runs smoothly.