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

Solution

1. Preparation

• Gather the necessary tools and parts.
• Disconnect the battery to prevent any electrical short circuits.
• Ensure the vehicle is parked on a level surface and secured with wheel chocks.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, torque wrench, penetrating oil.
• Sub-steps:
  1. Locate the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
  2. Apply penetrating oil to the sensor threads and let it sit for a few minutes.
  3. Using the O2 sensor socket, carefully remove both sensors.
  4. Install the new oxygen sensors by hand to avoid cross-threading, then tighten to manufacturer specifications (typically around 30 Nm).
  5. Reconnect the wiring harness to the new sensors.

3. Inspect the Catalytic Converter

• Tools Required: Jack and jack stands, exhaust pipe cutter (if needed).
• Sub-steps:
  1. Raise the vehicle using a jack and secure it with jack stands.
  2. Inspect the catalytic converter for physical damage, such as cracks or blockages.
  3. If the converter is damaged or clogged, remove the exhaust pipes using an exhaust pipe cutter or appropriate wrenches.
  4. Install a new catalytic converter, ensuring the gaskets are replaced, and tighten all connections to the specified torque.

4. Clear Codes and Test Drive

• Tools Required: OBD-II scanner.
• Sub-steps:
  1. Reconnect the battery and start the engine.
  2. Use an OBD-II scanner to clear the P0420 code from the vehicle’s computer.
  3. Take the vehicle for a test drive under various conditions to ensure the check engine light does not return.