why does my Ford Mustang S650 (2024-Present) have a check engine light with code P0420

Solution

1. Preparation

• Gather all necessary tools and parts.
• Disconnect the battery to prevent electrical shorts while working on the vehicle.
• Safety goggles and gloves should be worn.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, socket set, torque wrench.
• Remove the upstream oxygen sensor using the O2 sensor socket.
• Inspect the sensor for damage; replace if necessary.
• Install the new oxygen sensor and torque to manufacturer's specifications (typically around 30-35 lb-ft).
• Repeat for the downstream oxygen sensor if it shows signs of failure.

3. Inspect and Replace Catalytic Converter (if necessary)

• Tools Required: Wrench set, jack, jack stands, exhaust cut-off tool (if applicable).
• Raise the vehicle securely on jack stands.
• Remove the exhaust pipes connected to the catalytic converter after inspecting for damage.
• Unbolt the catalytic converter from its mounting points and remove it.
• Install the new catalytic converter, ensuring proper alignment and sealing.
• Reconnect the exhaust system, tightening all bolts to the manufacturer's torque specifications.

4. Clear Codes and Test Drive

• Reconnect the battery.
• Use the OBD-II scanner to erase the P0420 trouble code.
• Start the engine and allow it to reach operating temperature.
• Take the vehicle for a test drive to ensure the check engine light does not return.