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

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the vehicle is parked on a level surface, and the engine is cool.
• Disconnect the negative battery terminal.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, wrench set, multimeter.
• Remove the upstream oxygen sensor:
  1. Locate the upstream O2 sensor (before the catalytic converter).
  2. Use the O2 sensor socket to unscrew the sensor.
• Test the upstream sensor:
  1. Connect the multimeter probes to the sensor terminals.
  2. Start the engine and check for voltage fluctuation (should be between 0.1V to 0.9V).
• If the sensor is faulty, replace it with a new one:
  1. Apply anti-seize compound on the threads of the new sensor.
  2. Install the new sensor, tightening it to manufacturer specifications (usually around 30 ft-lbs).
• Repeat these steps for the downstream O2 sensor if needed.

3. Inspect and Replace Catalytic Converter

• Tools Required: Socket set, torque wrench, jack stands.
• Inspect the catalytic converter for damage or blockages:
  1. Visually check for dents, rust, or holes.
  2. If internal damage is suspected, perform a backpressure test.
• If the catalytic converter is faulty, replace it:
  1. Disconnect the exhaust pipes from the catalytic converter.
  2. Remove any mounting bolts or brackets securing the converter.
  3. Install the new catalytic converter, ensuring proper alignment.
  4. Torque the bolts to the manufacturer's specifications (typically around 30-40 ft-lbs).
  5. Reconnect the exhaust system.

4. Clear Codes and Test

• Reconnect the negative battery terminal.
• Use the OBD-II scanner to clear any fault codes.
• Test drive the vehicle for 20-30 minutes to check for any reoccurrence of the P0420 code.