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

Solution

1. Preparation

• Gather all necessary tools and parts.
• Disconnect the negative battery terminal to prevent electrical issues.

2. Inspect and Replace Oxygen Sensors

1. Locate the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
2. Disconnect the wiring harness from both sensors.
3. Remove the oxygen sensors using an O2 sensor socket or wrench.
4. Install new oxygen sensors, ensuring they are properly threaded and tightened to manufacturer specifications (typically 30-40 Nm).
5. Reconnect the wiring harness to each sensor.

3. Inspect and Replace the Catalytic Converter (if necessary)

1. Locate the catalytic converter in the exhaust system.
2. Remove any heat shields if applicable.
3. Unbolt the catalytic converter from the exhaust pipes using a socket set; be cautious of exhaust hangers.
4. Inspect the catalytic converter for physical damage or clogging.
5. Install a new catalytic converter, ensuring all gaskets are replaced and exhaust bolts are torqued to manufacturer specifications.
6. Reinstall any heat shields removed during the process.

4. Reconnect Battery and Clear Codes

1. Reconnect the negative battery terminal.
2. Use an OBD-II scanner to clear the P0420 code from the engine control unit (ECU).
3. Start the engine and allow it to reach operating temperature.