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

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the battery to prevent electrical shorts and ensure safety.
• Raise the vehicle and secure it on jack stands.

2. Inspect and Replace Oxygen Sensors (if necessary)

• Tools Required: O2 sensor socket, torque wrench
• Remove the pre-catalytic oxygen sensor:
  • Unplug the electrical connector.
  • Use the O2 sensor socket to remove the sensor from the exhaust manifold.
• If the post-catalytic sensor is also faulty, repeat the same process for it.
• Install new oxygen sensors:
  • Apply anti-seize compound to the threads (if recommended).
  • Torque to manufacturer specifications (typically around 30 Nm).
  • Reconnect electrical connectors.

3. Inspect and Replace Catalytic Converter (if necessary)

• Tools Required: Socket set, torque wrench, exhaust sealant
• Remove the faulty catalytic converter:
  • Unscrew and disconnect the exhaust pipes from the catalytic converter using the socket set.
  • Remove any mounting brackets or bolts securing the converter.
• Install the new catalytic converter:
  • Position the new converter in place.
  • Secure it using the original or new bolts and brackets, torquing to manufacturer specifications (usually around 50 Nm).
  • Apply exhaust sealant to ensure a leak-free connection.

4. Reset the Engine Control Unit (ECU)

• Reconnect the battery.
• Use an OBD-II scanner to clear the P0420 code from the ECU.
• Start the engine and allow it to reach operating temperature.