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

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the vehicle is parked on a flat surface and the engine is off.
• Disconnect the battery to avoid any electrical shorts.

2. Inspect Exhaust System

• Tools Required: Socket set, jack stands
• Sub-steps:
  1. Raise the vehicle using a jack and secure it with jack stands.
  2. Visually inspect the exhaust system from the engine to the tailpipe for any signs of leaks or damage.
  3. Repair or replace any damaged sections of the exhaust system.

3. Test and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, multimeter
• Sub-steps:
  1. Locate the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
  2. Disconnect the wiring harness from both sensors.
  3. Use a multimeter to test the voltage output of the upstream sensor (should fluctuate between 0.1V and 0.9V).
  4. If the readings are out of range, replace the faulty upstream oxygen sensor.
  5. Repeat testing for the downstream sensor. If faulty, replace it as well.

4. Replace Catalytic Converter (if necessary)

• Tools Required: Wrench set, exhaust pipe cutter (if applicable)
• Sub-steps:
  1. Remove the exhaust system components connected to the catalytic converter.
  2. Unbolt the catalytic converter from the exhaust manifold and exhaust pipe.
  3. Install the new catalytic converter, ensuring proper alignment.
  4. Reattach all exhaust components and check for secure fittings.

5. Reconnect Battery and Clear Codes

• Sub-steps:
  1. Reconnect the battery terminals.
  2. Use the OBD-II scanner to clear the P0420 code from the system.
  3. Start the vehicle and allow it to reach operating temperature.