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

Solution

1. Preparation

• Gather tools and parts.
• Disconnect the battery to prevent electrical shorts.
• Raise the vehicle on jack stands and ensure it is secure.

Tools Required:

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

2. Inspect and Replace Oxygen Sensors

1. Locate the Oxygen Sensors:

   • Identify the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.

2. Test the Sensors:

   • Use a multimeter to check the voltage output of both sensors. The upstream sensor should fluctuate between 0.1 to 0.9 volts while the engine is running.

3. Remove and Replace Defective Sensors:

   • Disconnect the wiring harness from the sensors.
   • Use a socket to remove the sensors. Install new sensors and torque them to the manufacturer specifications (typically around 30 Nm).
   • Reconnect the wiring harness.

3. Inspect and Replace Catalytic Converter

1. Remove the Exhaust Components:

   • Detach any mounting bolts and hangers securing the exhaust system.
   • If necessary, cut the exhaust pipe before and after the catalytic converter (if it's severely rusted).

2. Inspect the Catalytic Converter:

   • Look for signs of damage, such as rattling sounds or visible blockages.

3. Install New Catalytic Converter:

   • Position the new catalytic converter in place.
   • Reattach the exhaust system and secure with bolts, torquing to specifications.
   • Ensure all hangers and gaskets are replaced as needed.

4. Reconnect and Test

1. Reconnect Battery:

   • Ensure all connections are secure and reconnect the battery.

2. Clear Codes:

   • Use the OBD-II scanner to clear the P0420 code.

3. Test Drive:

   • Take the vehicle for a test drive to ensure that the check engine light does not return.