how to fix P0420 code on my Ford Mustang S650 (2024-Present)

Solution

1. Preparation

• Gather tools and parts needed for the repair.
• Disconnect the battery to prevent electrical issues.
• Allow the vehicle to cool down to avoid burns.

2. Inspect and Replace Faulty Components

• Oxygen Sensors:

  1. Locate the upstream and downstream oxygen sensors.
  2. Disconnect the wiring harness from each sensor.
  3. Use a sensor socket to remove the faulty oxygen sensors.
  4. Install new sensors, tightening to the manufacturer's specified torque (usually around 30 lb-ft).
  5. Reconnect the wiring harnesses.

• Catalytic Converter:

  1. Remove the exhaust heat shield if applicable.
  2. Unbolt the catalytic converter from the exhaust system, noting the orientation and position.
  3. Inspect the old catalytic converter for blockage or damage.
  4. Install the new catalytic converter, ensuring all gaskets are in place and tightening to manufacturer's specifications (usually around 40 lb-ft).
  5. Reinstall the heat shield if removed.

3. Clear Codes and Test

• Reconnect the battery.
• Use the OBD-II scanner to clear the P0420 code.
• Start the engine and allow it to reach operating temperature.