how to diagnose P0420 code in my Ford Mustang S650 (2024-Present)?

Solution

1. Preparation

• Gather tools and parts required for the repair.
• Ensure the vehicle is parked on a level surface and the ignition is turned off.
• Disconnect the negative battery terminal to prevent electrical issues.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, ratchet and extension, torque wrench.
• Remove the upstream (pre-catalytic converter) oxygen sensor:
  1. Use the O2 sensor socket to unscrew the sensor from the exhaust pipe.
  2. Inspect the thread and connector for damage.
  3. Install the new sensor, ensuring it is tightened to the manufacturer’s specified torque.
• Repeat for the downstream (post-catalytic converter) oxygen sensor if needed.

3. Inspect and Replace Catalytic Converter

• Tools Required: Socket set, torque wrench, exhaust hangers tool, possibly a torch for stubborn bolts.
• Remove the catalytic converter:
  1. Disconnect any exhaust hangers or brackets holding the converter in place.
  2. Unbolt the catalytic converter from the exhaust system, taking care to keep the gaskets and hardware for reuse if possible.
  3. Inspect the old catalytic converter for signs of damage or clogging.
  4. Install the new catalytic converter, ensuring to use new gaskets and tightening bolts to the specified torque.

4. Reconnect Battery and Clear Codes

• Reconnect the negative battery terminal.
• Use the OBD-II scanner to clear the trouble codes.

5. Test Drive and Monitor

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