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

Solution

1. Preparation

• Gather tools and parts.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Allow the engine to cool down completely before beginning work.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, wrench set, multimeter.
• Inspect the upstream and downstream oxygen sensors for any signs of damage or corrosion.
• If either sensor is faulty, remove it using the O2 sensor socket and replace it with a new one.
• Torque the new sensor to the manufacturer’s specified value (typically around 30 lb-ft).

3. Inspect the Catalytic Converter

• Tools Required: Visual inspection tools, exhaust pipe cutter (if needed).
• Visually inspect the catalytic converter for any signs of damage or blockage.
• If damage is found, remove the catalytic converter by cutting the exhaust pipes if necessary, and replace it with a new unit.
• Ensure proper alignment and secure the new catalytic converter with appropriate clamps and gaskets.

4. Clear the Code and Test

• Reconnect the negative battery terminal.
• Use the OBD-II scanner to clear the P0420 code from the vehicle’s computer.
• Start the engine and allow it to reach operating temperature.
• Take the vehicle for a test drive to ensure normal operation.