how to fix P0420 code in Honda Civic 10th Generation (2016-2021)

Solution

1. Preparation

• Ensure the vehicle is parked on a level surface and the engine is turned off.
• Gather tools such as a jack, jack stands, OBD-II scanner, multimeter, socket set, and safety equipment (gloves, goggles).

2. Address any Exhaust Leaks

• Sub-steps:
  1. If any leaks are found during the inspection, use exhaust repair tape or replace damaged sections of the exhaust pipe.
  2. Tighten any loose clamps or fittings that may be causing leaks.

3. Test and Replace Oxygen Sensors

• Sub-steps:
  1. Disconnect the electrical connector from the upstream and downstream oxygen sensors.
  2. Use a multimeter to measure the voltage output of the sensors. The upstream sensor should fluctuate between 0.1 and 0.9 volts, while the downstream sensor should have a more stable output.
  3. If the sensor readings are outside these values, replace the faulty oxygen sensors with OEM or quality aftermarket sensors.
  4. Reconnect the sensors.

4. Inspect and Replace the Catalytic Converter

• Sub-steps:
  1. If the oxygen sensors are functioning correctly, check the catalytic converter for clogging or damage.
  2. Remove the catalytic converter by loosening the bolts or clamps securing it to the exhaust system.
  3. Inspect the internal structure of the catalytic converter. If it is damaged or heavily clogged, replace it with a new catalytic converter.
  4. Install the new catalytic converter and ensure all bolts are torqued to manufacturer specifications.

5. Clear Codes and Test Drive

• Sub-steps:
  1. Use the OBD-II scanner to clear the P0420 code from the vehicle's computer.
  2. Start the engine and allow it to reach operating temperature.
  3. Take the vehicle for a test drive to ensure the check engine light does not reappear.