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

Solution

1. Preparation

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

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 Sensors: Use an oxygen sensor socket to carefully unscrew and remove both sensors.
3. Inspect the Wiring: Check the wiring harness for any fraying or damage. Repair as necessary.
4. Install New Sensors: Apply anti-seize compound to the threads of the new sensors and install them securely, ensuring not to overtighten.
5. Reconnect the Wiring: Plug in the electrical connectors for both sensors.

3. Inspect and Replace Catalytic Converter (if necessary)

1. Remove Exhaust Components: Depending on your model, you may need to remove the exhaust pipe or heat shields to access the catalytic converter.
2. Unbolt the Catalytic Converter: Use appropriate socket sizes to remove the bolts securing the catalytic converter to the exhaust manifold and downstream exhaust.
3. Inspect the Old Catalytic Converter: Check for signs of clogging, melting, or contamination. If any damage is found, replace the catalytic converter.
4. Install New Catalytic Converter: Position the new catalytic converter in place and secure it with the original bolts. Ensure proper alignment.
5. Reconnect Exhaust Components: Reattach any exhaust pipes or heat shields removed during the process.

4. Clear Codes and Test Drive

1. Reconnect Battery: Reconnect the negative battery terminal.
2. Clear the Codes: Use the OBD-II scanner to clear the P0420 code from the system.
3. Test Drive: Drive the vehicle for a few miles under various conditions to ensure the check engine light does not reappear.