how to fix P0420 code on Honda Accord 10th Generation (2018-2022)

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure safety gear (gloves, goggles) is worn.
• Disconnect the negative battery terminal to prevent electrical shorts.

2. Inspect and Test Oxygen Sensors

• Tools Required: OBD-II scanner, multimeter
• Check the wiring and connectors of both oxygen sensors for damage or corrosion.
• Use a multimeter to test the upstream oxygen sensor:
  • Start the engine and allow it to reach operating temperature.
  • Measure the voltage output; it should fluctuate between 0.1V and 0.9V.
• Repeat the test for the downstream oxygen sensor; it should be relatively stable (0.5V-0.7V).

3. Replace Faulty Oxygen Sensors (if necessary)

• If either sensor is faulty, replace it:
  • Sub-steps:
    • Remove the sensor using an oxygen sensor socket.
    • Apply anti-seize compound to the threads of the new sensor.
    • Install the new sensor and torque it to the manufacturer's specifications (typically around 30 ft-lbs).
• Reconnect the negative battery terminal.

4. Inspect and Replace Catalytic Converter (if necessary)

• Tools Required: Socket set, jack and jack stands
• If the catalytic converter is damaged or clogged:
  • Raise the vehicle and secure with jack stands.
  • Disconnect the exhaust system at the flanges using the socket set.
  • Remove the catalytic converter from the mounting brackets and exhaust pipes.
  • Install the new catalytic converter, ensuring proper alignment and securing all bolts to manufacturer specifications.
  • Reconnect the exhaust system.

5. Clear Codes and Test Drive

• Use the OBD-II scanner to clear the P0420 code.
• Test drive the vehicle for at least 20 miles under varied driving conditions to ensure the check engine light does not reappear.