how to fix the P0420 code on my Ford Explorer Sixth Generation (2020-present)

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the vehicle battery to ensure safety.

2. Inspect Oxygen Sensors

• Remove the upstream and downstream oxygen sensors using an O2 sensor socket.
• Inspect the sensors for damage or contamination.
• If defective, replace the sensors with OEM-quality replacements.

3. Check Exhaust System

• Visually inspect the exhaust pipes, joints, and the catalytic converter for any signs of leaks or cracks.
• Repair or replace any damaged sections of the exhaust system.

4. Test Catalytic Converter

• If the catalytic converter is suspected to be faulty, perform a back pressure test:
  • Insert a back pressure gauge into the O2 sensor port (upstream).
  • Start the engine and observe pressure readings; a reading above 1.5 psi at idle indicates a clogged catalytic converter.
• If the converter is clogged, replace it with a new unit.

5. Reassemble and Reconnect

• Reinstall the O2 sensors (if removed) and ensure they are properly connected.
• Reconnect the vehicle battery.
• Clear the engine codes using the OBD-II scanner.