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

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the battery to ensure safety during repairs.
• Raise the vehicle using a jack and secure it with jack stands.

2. Inspect and Replace Oxygen Sensors

1. Locate the oxygen sensors: Identify the upstream (pre-catalytic converter) and downstream (post-catalytic converter) oxygen sensors.
2. Remove the upstream oxygen sensor:
   • Use an oxygen sensor socket to unscrew and remove the sensor.
   • Disconnect the electrical connector.
3. Install the new upstream oxygen sensor:
   • Apply anti-seize compound to the threads of the new sensor.
   • Install and tighten to manufacturer specifications (usually around 30 Nm).
   • Reconnect the electrical connector.
4. Repeat for the downstream oxygen sensor following the same procedure.

3. Inspect and Replace Catalytic Converter (if necessary)

1. Remove exhaust components: Detach any exhaust hangers or clamps connected to the catalytic converter.
2. Remove the catalytic converter:
   • Unbolt the catalytic converter from the exhaust manifold and the exhaust pipe.
   • Carefully take out the old catalytic converter.
3. Install the new catalytic converter:
   • Position the new catalytic converter in place.
   • Bolt it to the exhaust manifold and exhaust pipe, ensuring a secure fit (torque to specifications).
4. Reattach exhaust hangers/clamps to ensure everything is secured properly.

4. Reset the Engine Control Module (ECM)

1. Reconnect the battery after all repairs.
2. Use the OBD-II scanner to clear the P0420 code from the ECM.