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 negative battery terminal to prevent electrical issues.
• Allow the engine to cool before working on the exhaust system.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, torque wrench, penetrating oil
• Remove the upstream and downstream oxygen sensors using the O2 sensor socket.
• Inspect the sensors for signs of damage or contamination.
• If faulty, install new oxygen sensors and torque them to the manufacturer’s specifications (usually around 30 Nm).

3. Inspect and Replace the Catalytic Converter

• Tools Required: Socket set, torque wrench, exhaust hanger removal tool
• Remove any exhaust clamps and bolts securing the catalytic converter to the exhaust system.
• Use the exhaust hanger removal tool to detach the catalytic converter from the hangers.
• Inspect the old catalytic converter for blockages or physical damage.
• Install the new catalytic converter and secure it with bolts, torquing to the manufacturer’s specifications (typically around 40 Nm).
• Reattach any exhaust clamps and hangers.

4. Clear Error Codes

• Reconnect the negative battery terminal.
• Use the OBD-II scanner to clear the P0420 code and any other related codes.