how to fix P0420 code on BMW 5 Series F10/F11 (2010-2017)

Solution

1. Preparation

• Gather tools and parts required for the repair.
• Disconnect the battery to prevent electrical shorts.
• Raise the vehicle safely using a jack and secure with jack stands.

2. Inspect and Replace Oxygen Sensors

1. Remove the O2 Sensors:

   • Tools: O2 sensor socket and ratchet.
   • Carefully unplug the electrical connectors from the upstream and downstream O2 sensors.
   • Use the O2 sensor socket to unscrew and remove the sensors from the exhaust system.

2. Install New O2 Sensors:

   • Apply anti-seize compound to the threads of the new O2 sensors.
   • Install the new sensors and tighten to manufacturer specifications (usually around 30 ft-lbs).
   • Reconnect the electrical connectors securely.

3. Inspect and Replace Catalytic Converter (if necessary)

1. Remove the Old Catalytic Converter:

   • Tools: Socket set, torque wrench, and possibly a cutting tool if flanges are rusted.
   • Remove any heat shields that obstruct access.
   • Disconnect the catalytic converter from the exhaust manifold and the exhaust pipe, ensuring to remove any mounting bolts and clamps.

2. Install New Catalytic Converter:

   • Position the new catalytic converter in place.
   • Securely fasten it to the exhaust manifold and pipe using new gaskets and bolts, torquing to manufacturer specifications (typically around 30-40 ft-lbs).
   • Reinstall any heat shields that were removed.

4. Final Checks

• Reconnect the battery.
• Clear the P0420 code using the OBD-II scanner.
• Start the engine and allow it to reach operating temperature.