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

Solution

1. Preparation

• Gather all necessary tools and parts.
• Park the vehicle on a flat surface and engage the parking brake.
• Disconnect the battery to ensure safety while working on electrical components.

2. Inspect and Replace Oxygen Sensors (if necessary)

• Tools Required: O2 sensor socket, ratchet, torque wrench, penetrating oil.
• Locate the upstream (pre-catalytic converter) and downstream (post-catalytic converter) oxygen sensors.
• Apply penetrating oil to the sensor threads and allow it to soak for a few minutes.
• Use the O2 sensor socket to remove the upstream oxygen sensor.
• Install the new oxygen sensor, ensuring to torque it to manufacturer specifications (typically around 30 Nm).
• Repeat the process for the downstream oxygen sensor if it is also faulty.

3. Inspect and Replace Catalytic Converter (if necessary)

• Tools Required: Socket set, torque wrench, exhaust pipe cutter, gasket scraper.
• Remove the exhaust pipe from the catalytic converter by loosening the bolts and using a socket set.
• Carefully inspect the catalytic converter for clogs or damage; if necessary, proceed to replace it.
• Use the exhaust pipe cutter to remove the old catalytic converter.
• Install the new catalytic converter, ensuring all gaskets are replaced and torquing the bolts to the specified values.
• Reattach the exhaust pipe and ensure all connections are secure.

4. Reset the Engine Control Module (ECM)

• Reconnect the battery.
• Use the OBD-II scanner to clear the P0420 code from the ECM.
• Start the engine and allow it to reach operating temperature, ensuring the check engine light does not reappear.