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

Solution

1. Preparation

• Tools Required: OBD-II scanner, jack and jack stands, wrench set, multimeter, safety glasses, gloves.
• Sub-steps:
  • Park the vehicle on a level surface and engage the parking brake.
  • Disconnect the negative battery terminal to prevent electrical shorts.
  • Raise the vehicle using a jack and secure it with jack stands.

2. Inspect Exhaust System

• Sub-steps:
  • Visually inspect the exhaust system for any leaks, especially around the joints and the catalytic converter.
  • If leaks are found, repair or replace the affected components.

3. Check Oxygen Sensors

• Sub-steps:
  • Locate the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
  • Use a multimeter to measure the voltage output of both sensors while the engine is running.
  • Typically, the upstream sensor should fluctuate between 0.1V and 0.9V, while the downstream sensor should remain relatively stable. If abnormal readings are found, replace the faulty sensor.

4. Inspect and Clean Catalytic Converter

• Sub-steps:
  • If the catalytic converter appears contaminated or clogged, consider using a catalytic converter cleaner as per the product instructions.
  • If cleaning does not resolve the issue, the catalytic converter may need to be replaced.

5. Replace Catalytic Converter (if necessary)

• Sub-steps:
  • Remove any bolts or clamps securing the catalytic converter to the exhaust system.
  • Carefully detach the catalytic converter and install the new unit, ensuring proper alignment.
  • Tighten all bolts to the manufacturer's specified torque settings (usually around 30-40 lb-ft, check the service manual).

6. Reassemble and Test

• Sub-steps:
  • Reconnect the negative battery terminal.
  • Start the engine and allow it to run for a few minutes.
  • Clear any existing codes using the OBD-II scanner.
  • Perform a test drive to ensure the P0420 code does not reappear.