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

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the negative battery terminal to prevent electrical shorts.

2. Inspect and Replace Oxygen Sensors (if faulty)

• Tools Required: O2 sensor socket, ratchet, torque wrench.
• Remove the upstream oxygen sensor by unscrewing it with the O2 sensor socket.
• Install the new oxygen sensor and torque it to the manufacturer's specifications (usually around 30 lb-ft).
• Repeat the process for the downstream sensor if it is also faulty.

3. Replace Catalytic Converter (if necessary)

• Tools Required: Socket set, torque wrench, exhaust hanger removal tool.
• Remove any heat shields or covers obstructing access to the catalytic converter.
• Use the socket set to unbolt the catalytic converter from the exhaust piping.
• Disconnect any exhaust hangers using the exhaust hanger removal tool.
• Install the new catalytic converter, ensuring all gaskets are in place, and torque the bolts to the manufacturer's specifications.
• Reinstall any heat shields or covers removed earlier.

4. Reset the ECM

• Reconnect the negative battery terminal.
• Use the OBD-II scanner to clear the P0420 code from the ECM.

5. Test Drive

• Drive the vehicle for a test period to monitor for the return of the check engine light and ensure proper operation.