how to troubleshoot P0420 code on BMW 5 Series G30/G31 (2017-2024)

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the vehicle is parked on a level surface and the engine is cool.
• Disconnect the battery for safety.

2. Inspect Oxygen Sensors

• Tools Required: OBD-II scanner, multimeter
• Using the OBD-II scanner, monitor the voltage output of the upstream and downstream oxygen sensors while the engine is running.
• Replace any faulty oxygen sensors if the readings are outside the manufacturer specifications.

3. Check and Replace Catalytic Converter

• Tools Required: Socket set, torque wrench, exhaust pipe cutter (if needed)
• Remove the exhaust components connected to the catalytic converter.
  • Carefully detach any brackets or hangers.
  • Use the socket set to remove the bolts securing the catalytic converter.
• Inspect the catalytic converter for physical damage or clogging.
• If necessary, replace the catalytic converter with a new, OEM or high-quality aftermarket unit.
  • Ensure proper alignment and torque all bolts to manufacturer specifications.

4. Reconnect Components

• Reattach any exhaust components removed during the inspection.
• Reconnect the battery and clear any existing codes using the OBD-II scanner.