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

Solution

1. Preparation

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

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, torque wrench, penetrating oil
• Remove the downstream oxygen sensor (after the catalytic converter):
  • Apply penetrating oil to the sensor threads if needed.
  • Use the O2 sensor socket to unscrew the sensor.
• Install the new oxygen sensor:
  • Hand-tighten the new sensor into place.
  • Use the torque wrench to tighten to the manufacturer’s specification (typically around 30 Nm).
• Repeat for the upstream oxygen sensor if necessary.

3. Examine and Replace Catalytic Converter

• Tools Required: Socket set, torque wrench, gaskets
• Disconnect the exhaust from the catalytic converter:
  • Loosen the exhaust clamps and bolts.
  • Carefully detach the exhaust pipes.
• Remove the old catalytic converter:
  • Unscrew the mounting bolts securing the catalytic converter to the exhaust manifold and the exhaust pipe.
• Install the new catalytic converter:
  • Position the new catalytic converter and secure it using the original or new gaskets.
  • Torque the bolts to the manufacturer’s specifications.
• Reattach the exhaust system, ensuring all connections are tight and leak-free.

4. Clear Codes and Test

• Reconnect the battery.
• Use an OBD-II scanner to clear the P0420 code.
• Start the engine and allow it to reach operating temperature.