how to diagnose Honda Civic 10th Generation (2016-2021) check engine light with codes P0420

Solution

1. Preparation

• Gather tools and parts needed for the repair.
• Disconnect the battery to ensure safety while working on the electrical systems.
• Tools Required: OBD-II scanner, multimeter, socket set, torque wrench.

2. Inspect and Replace Oxygen Sensors (if faulty)

• Remove the upstream and downstream oxygen sensors using the appropriate socket.
• Inspect the wiring for any damage or corrosion.
• Install new oxygen sensors:
  • Ensure the threads are clean and apply anti-seize compound to the sensor threads.
  • Torque the sensors to the manufacturer’s specifications (usually around 30-40 lb-ft).
• Reconnect the battery.

3. Replace Catalytic Converter (if necessary)

• Safely lift the vehicle and support it with jack stands.
• Disconnect the exhaust system from the catalytic converter, removing any bolts or clamps.
• Remove the old catalytic converter.
• Install the new catalytic converter:
  • Ensure all gaskets are replaced.
  • Torque the bolts to manufacturer specifications (typically 25-30 lb-ft).
• Reconnect the exhaust system and check for leaks.

4. Clear Codes and Test Drive

• Use the OBD-II scanner to clear the stored trouble codes.
• Perform a test drive under varied driving conditions to ensure the Check Engine Light does not return.