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

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the vehicle is parked on a level surface and the engine is cool.
• Disconnect the battery to avoid any electrical shorts.

Tools Required:

• OBD-II scanner
• Multimeter
• Socket set
• Torque wrench
• Vacuum gauge

2. Inspect and Replace Oxygen Sensors (if necessary)

1. Locate the Sensors: Identify the upstream and downstream oxygen sensors. The upstream sensor is typically located before the catalytic converter, while the downstream sensor is after it.
2. Remove the Sensors: Use a socket wrench to carefully unscrew the sensors. Be cautious of any wiring connected to them.
3. Test the Sensors: Use a multimeter to measure the resistance and voltage output of both sensors. Replace the sensor showing faulty readings.
4. Install New Sensors: Thread the new sensors into place and tighten them to the manufacturer's specifications (usually around 30 Nm).
5. Reconnect Wiring: Ensure all wiring harnesses are securely connected.

3. Inspect and Replace Catalytic Converter (if necessary)

1. Remove Exhaust Components: If the catalytic converter needs to be replaced, remove any exhaust pipes or hangers connected to it using a socket set.
2. Unbolt the Catalytic Converter: Locate the bolts securing the catalytic converter to the exhaust manifold and exhaust pipes. Use a torque wrench to carefully remove these bolts.
3. Replace with New Catalytic Converter: Position the new catalytic converter into place and secure it with the previously removed bolts, tightening them to the specified torque (typically around 40 Nm).
4. Reattach Exhaust Components: Reinstall any exhaust pipes or hangers that were removed earlier, ensuring all connections are tight.

4. Clear Codes and Test Drive

1. Reconnect the Battery: Once repairs are complete, reconnect the vehicle's battery.
2. Clear the Codes: Use the OBD-II scanner to clear the P0420 code from the ECM.
3. Test Drive the Vehicle: Drive the vehicle under various conditions to ensure that the check engine light does not reappear.