how to fix P0420 code on BMW 3 Series F30/F31 (2012-2019)

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the battery to ensure safety during repairs.

2. Inspect and Replace Oxygen Sensors

1. Remove the O2 Sensors:

   • Use an O2 sensor socket to carefully unscrew the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
   • Ensure to disconnect the electrical connectors before removal.

2. Install New O2 Sensors:

   • Apply anti-seize compound on the threads of the new sensors.
   • Install the new sensors by hand, then tighten to the manufacturer's specifications (usually around 30 Nm).

3. Inspect and Replace Catalytic Converter

1. Remove Exhaust Components:

   • If necessary, remove any exhaust shields or components blocking access to the catalytic converter using a socket set.
   • Use penetrating oil on bolts if they are rusted.

2. Remove the Catalytic Converter:

   • Unbolt the catalytic converter from the exhaust manifold and exhaust pipe.
   • Carefully remove it from the vehicle.

3. Install New Catalytic Converter:

   • Position the new catalytic converter in place.
   • Tighten all bolts to the manufacturer’s torque specifications (typically around 40-50 Nm).

4. Reconnect Battery and Clear Codes

1. Reconnect the battery and ensure all connections are secure.
2. Use an OBD-II scanner to clear the P0420 code from the system.