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

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the battery to prevent electrical shorts during repairs.
• Allow the exhaust system to cool before working on it.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, torque wrench
• Sub-steps:
  1. Locate the upstream and downstream oxygen sensors (pre-cat and post-cat).
  2. Disconnect the electrical connectors from both sensors.
  3. Use the O2 sensor socket to remove the sensors from their respective exhaust pipes.
  4. Install new oxygen sensors by threading them into the exhaust and tightening them to the manufacturer's specified torque (typically around 30 lb-ft).
  5. Reconnect the electrical connectors to the sensors.

3. Inspect and Replace Catalytic Converter

• Tools Required: Socket set, cutting tool (if necessary), gasket scraper, torque wrench
• Sub-steps:
  1. Remove any heat shields covering the catalytic converter.
  2. Disconnect the exhaust pipes connected to the catalytic converter using the socket set.
  3. If required, cut the old catalytic converter out, ensuring clean cuts for proper fitment.
  4. Install the new catalytic converter, ensuring proper alignment and sealing.
  5. Reattach the exhaust pipes and tighten the bolts to the specified torque (refer to the service manual).
  6. Reinstall any heat shields removed earlier.

4. Clear Codes and Test Drive

• Tools Required: OBD-II scanner
• Sub-steps:
  1. Reconnect the battery.
  2. Use the OBD-II scanner to clear the P0420 code from the vehicle’s computer.
  3. Start the engine and let it idle for a few minutes.
  4. Take the vehicle for a test drive to ensure the check engine light does not return.