how to fix P0421 code in BMW X5 G05 (2019-2024)

Solution

1. Preparation

• Ensure the vehicle is parked on a level surface, and the engine is cool.
• Gather tools and safety equipment: gloves, safety glasses, OBD-II scanner, multimeter, socket set, jack stands.

2. Inspect and Replace Oxygen Sensors

• Sub-steps:
  1. Disconnect the battery to prevent electrical shorts.
  2. Locate the upstream and downstream oxygen sensors in the exhaust system.
  3. Use a socket wrench to remove the oxygen sensors.
  4. Inspect the sensor tips for contamination or damage.
  5. Install new oxygen sensors and tighten to manufacturer specifications (usually around 30 Nm).
  6. Reconnect the battery.

3. Check and Replace Catalytic Converter (if necessary)

• Sub-steps:
  1. If the catalytic converter is suspected to be damaged, disconnect the exhaust pipes leading to and from the converter.
  2. Remove any brackets or heat shields securing the catalytic converter.
  3. Replace the catalytic converter with an OEM or high-quality aftermarket unit.
  4. Reinstall all components, ensuring proper fit and torque specifications.

4. Clear Codes and Test

• Sub-steps:
  1. Use the OBD-II scanner to clear the P0421 code from the vehicle's computer.
  2. Start the engine and allow it to reach operating temperature.
  3. Perform a test drive to ensure the vehicle operates normally and recheck for any error codes.