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

Solution

1. Preparation

• Gather tools and parts necessary for the repair.
• Disconnect the battery to ensure safety while working on the vehicle.

2. Inspect and Replace Oxygen Sensors (if needed)

• Tools Required: O2 sensor socket, ratchet, torque wrench
• Remove the upstream oxygen sensor:
  • Use the O2 sensor socket to unscrew the sensor from the exhaust manifold.
• Install the new upstream oxygen sensor:
  • Apply anti-seize compound to the threads of the new sensor.
  • Torque to manufacturer specifications (typically around 30 ft-lbs).
• Repeat for the downstream oxygen sensor if it was found faulty.

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

• Tools Required: Socket set, jack and jack stands, exhaust pipe cutter (if necessary)
• Raise the vehicle securely using jack stands.
• Remove any heat shields or brackets obstructing access to the catalytic converter.
• Disconnect the exhaust pipes from the catalytic converter:
  • Cut the exhaust pipe if necessary, and use a wrench to unbolt any connections.
• Remove the catalytic converter:
  • Unscrew the bolts holding the converter in place.
• Install the new catalytic converter:
  • Position the new converter and secure it with the bolts.
  • Reconnect the exhaust pipes, ensuring they are properly sealed.
• Reinstall any heat shields or brackets.