how to fix P0420 code in Ford Mustang S550 (2015-2023)

Solution

1. Preparation

• Gather tools and parts needed for repairs.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Allow the exhaust system to cool before working on it.

2. Inspect and Replace Oxygen Sensors (if necessary)

• Tools Required: O2 sensor socket, wrench set, torque wrench
• Remove the upstream oxygen sensor from the exhaust manifold using the O2 sensor socket.
• Install the new upstream oxygen sensor, tightening it to the manufacturer's specified torque (typically around 30 lb-ft).
• Repeat the process for the downstream oxygen sensor if it's also faulty.

3. Inspect and Replace Catalytic Converter (if necessary)

• Tools Required: Socket set, pipe cutter or saw, exhaust gasket, torque wrench
• Disconnect the exhaust pipes from the catalytic converter by removing the bolts with a socket set.
• Use a pipe cutter or saw to remove any sections of pipe that may be damaged or corroded.
• Install the new catalytic converter with a new exhaust gasket, ensuring all bolts are tightened to the manufacturer's torque specifications (usually around 40 lb-ft).
• Reconnect the exhaust pipes securely.

4. Clear Error Codes

• Reconnect the negative battery terminal.
• Use the OBD-II scanner to clear the P0420 code from the vehicle's computer.
• Perform a drive cycle as specified in the service manual to allow the vehicle to re-evaluate the catalytic converter's performance.