how to fix 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.
• Allow the engine to cool before beginning work.

2. Inspect and Replace Oxygen Sensors

1. Locate the Sensors:
   • Identify the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
2. Remove the Sensors:
   • Use an oxygen sensor socket to carefully unscrew the sensors.
   • Disconnect the electrical connectors.
3. Install New Sensors:
   • Apply anti-seize compound to the threads of the new sensors.
   • Screw in the new sensors and connect the electrical connectors.
   • Torque to manufacturer specifications (typically around 30 ft-lbs).

3. Inspect and Replace Catalytic Converter

1. Remove Exhaust Components:
   • Unbolt any heat shields or exhaust pipes connected to the catalytic converter.
   • Use a socket set to remove the nuts/bolts securing the converter.
2. Inspect the Old Converter:
   • Check for physical damage or signs of failure (e.g., rattling).
3. Install the New Catalytic Converter:
   • Position the new catalytic converter in place and secure it with bolts.
   • Reattach any exhaust components and heat shields, ensuring all connections are tight.
   • Torque bolts to manufacturer specifications (consult repair manual).

4. Reset the Engine Control Module (ECM)

1. Reconnect the Battery:
   • Reattach the negative battery terminal.
2. Clear Error Codes:
   • Use the OBD-II scanner to clear the P0420 code and any other related codes.
3. Test Drive:
   • Perform a test drive to ensure that the engine runs smoothly and the check engine light does not reappear.