how to fix P0420 code on my Ford Explorer Fifth Generation (2011-2019)

Solution

1. Preparation

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

2. Inspect and Test Oxygen Sensors

• Tools Required: OBD-II scanner, multimeter
• Remove the upstream (pre-catalytic converter) oxygen sensor using an oxygen sensor socket.
• Connect the multimeter to measure the voltage output while the engine is running.
• Repeat the process for the downstream (post-catalytic converter) oxygen sensor.
• If either sensor is out of spec (typically 0.1V to 0.9V for the upstream sensor during operation), replace that sensor.

3. Replace Catalytic Converter (if necessary)

• Tools Required: Socket set, torque wrench, exhaust gasket
• If the oxygen sensors are functioning correctly, and the catalytic converter is confirmed defective:
  1. Raise the vehicle and secure it with jack stands.
  2. Remove the exhaust pipe bolts attaching the catalytic converter to the exhaust system.
  3. Disconnect any heat shields or brackets holding the catalytic converter.
  4. Remove the old catalytic converter and clean the mounting surfaces on the exhaust system.
  5. Install the new catalytic converter and secure it with new gaskets and bolts.
  6. Torque the bolts to the manufacturer's specifications (typically around 30-40 lb-ft depending on the model).

4. Reconnect Battery and Clear Codes

• Reconnect the negative battery terminal.
• Use the OBD-II scanner to clear the P0420 code.
• Start the engine and let it idle for a few minutes to check for any reoccurring codes.