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

Solution

1. Preparation

• Gather tools and parts needed for the repair.
• Disconnect the battery to ensure safety while working on the vehicle.
• Raise the vehicle and secure it with jack stands.

2. Inspect and Replace Oxygen Sensors (if necessary)

• Tools Required: O2 sensor socket, ratchet, torque wrench.
• Remove the upstream (pre-catalytic converter) oxygen sensor:
  • Disconnect the electrical connector.
  • Use the O2 sensor socket to unscrew the sensor.
• Install the new oxygen sensor:
  • Apply anti-seize compound to the threads (if required).
  • Torque to manufacturer specifications (typically around 30 lb-ft).
• Repeat for the downstream (post-catalytic converter) oxygen sensor.

3. Inspect and Replace the Catalytic Converter (if necessary)

• Tools Required: Socket set, wrench set, exhaust hanger removal tool.
• Remove the catalytic converter:
  • Disconnect the exhaust pipes at both ends of the catalytic converter.
  • Remove any mounting brackets or hangers.
• Install the new catalytic converter:
  • Position the new unit and secure it with the brackets.
  • Reconnect the exhaust pipes, ensuring all connections are tight.
• Torque all bolts to manufacturer specifications.

4. Clear the Codes

• Reconnect the battery.
• Use the OBD-II scanner to clear the P0420 code from the vehicle's computer.