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

Solution

1. Preparation

• Gather tools: OBD-II scanner, multimeter, infrared thermometer, socket set, jack and jack stands.
• Ensure the vehicle is parked on a flat surface, and the engine is cool.
• Disconnect the battery to avoid any electrical shorts.

2. Inspect and Replace Oxygen Sensors

1. Locate the oxygen sensors: The upstream sensor is before the catalytic converter, and the downstream is after it.
2. Remove the upstream and downstream oxygen sensors: Use a socket wrench to unscrew the sensors carefully.
3. Test the sensors: Use a multimeter to check the voltage output of the upstream sensor (should fluctuate between 0.1 to 0.9 volts). Replace any faulty sensors.
4. Install new sensors: Apply anti-seize compound on the threads and torque to manufacturer's specifications (usually around 30-40 ft-lbs).

3. Inspect and Replace Catalytic Converter

1. Remove the exhaust system components: Loosen and detach exhaust clamps, and remove any hangers supporting the exhaust.
2. Unbolt the catalytic converter: Use a socket set to detach it from the exhaust manifold and the exhaust pipe.
3. Inspect the old converter: Check for any physical damage or clogging; if damaged, obtain a replacement.
4. Install the new catalytic converter: Position it properly and secure it using the bolts, tightening to the specified torque (typically around 40-50 ft-lbs).
5. Reattach exhaust components: Ensure all clamps and hangers are reinstalled securely.

4. Clear Codes and Test

1. Reconnect the battery: Ensure all connections are secure.
2. Clear the P0420 code: Use the OBD-II scanner to reset the check engine light.
3. Test drive: Drive the vehicle under varied conditions to monitor performance.