how to fix P0420 code on BMW X3 G01 (2018-2024)

Solution

1. Preparation

• Tools Required: OBD-II scanner, infrared thermometer, socket set, torque wrench, jack and jack stands.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Allow the engine to cool down.

2. Inspect and Replace Catalytic Converter

1. Remove Exhaust Components:
   • Raise the vehicle securely on jack stands.
   • Remove any exhaust heat shields if present.
   • Loosen the bolts connecting the catalytic converter to the exhaust system using a socket set.
2. Remove the Catalytic Converter:
   • Carefully detach the catalytic converter from the exhaust manifold and the downstream pipe.
   • If the converter is welded, use a saw to cut it out.
3. Install New Catalytic Converter:
   • Position the new catalytic converter in place, ensuring proper orientation.
   • Use a torque wrench to tighten the bolts to the manufacturer's specified torque setting (typically around 30-40 Nm, but refer to service manual).
   • Reinstall any heat shields removed earlier.

3. Inspect and Replace Oxygen Sensors (if necessary)

1. Remove the Oxygen Sensors:
   • Locate the upstream and downstream oxygen sensors attached to the catalytic converter.
   • Use an O2 sensor socket to remove the sensors, turning counterclockwise.
2. Install New Oxygen Sensors:
   • Apply anti-seize compound (if required) to the threads of new sensors.
   • Install the new sensors by threading them into the exhaust system and tightening securely.