how do I diagnose a P0420 code on my Ford Explorer Fifth Generation (2011-2019)

Solution

1. Preparation

• Tools Required: OBD-II scanner, infrared thermometer, wrench set, multimeter, safety glasses, gloves.
• Disconnect the battery before starting any work.
• Lift the vehicle safely using jack stands if necessary.

2. Inspect and Replace Oxygen Sensors

• Sub-steps:
  1. Locate the upstream (pre-catalytic converter) and downstream (post-catalytic converter) oxygen sensors.
  2. Unplug the electrical connectors from both sensors.
  3. Using an oxygen sensor socket, carefully remove both sensors.
  4. Install new oxygen sensors, ensuring they are properly torqued to manufacturer specifications (typically around 30 lb-ft).
  5. Reconnect the electrical connectors.

3. Inspect and Replace Catalytic Converter

• Sub-steps:
  1. Inspect the catalytic converter for physical damage or blockage.
  2. If replacement is necessary, unbolt the catalytic converter from the exhaust system using the appropriate wrench.
  3. Remove the old catalytic converter and install the new unit, ensuring that all gaskets are replaced and bolts are tightened to specification.
  4. Reconnect any exhaust hangers or heat shields that were removed during the process.

4. Clear Codes and Test Drive

• Sub-steps:
  1. Reconnect the battery and use the OBD-II scanner to clear the diagnostic trouble codes.
  2. Take the vehicle for a test drive to allow the engine to reach operating temperature and check for any reoccurrence of the P0420 code.