how to fix P0420 code on Honda Accord 8th Generation (2008-2012)

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the vehicle is parked on a level surface and the engine is cool.
• Disconnect the battery to prevent electrical issues.

2. Inspect and Replace Oxygen Sensors

1. Locate Oxygen Sensors: Find the upstream (before the catalytic converter) and downstream (after the catalytic converter) oxygen sensors.
2. Remove Sensors:
   • Use an oxygen sensor socket to carefully remove the sensors.
   • Disconnect the wiring harness from each sensor.
3. Install New Sensors:
   • Apply anti-seize compound to the threads of the new sensors.
   • Screw the new sensors into place and reconnect the wiring harness.
   • Torque to manufacturer specifications (typically around 30 lb-ft).

3. Inspect the Catalytic Converter

1. Check for Damage: Examine the catalytic converter for any signs of physical damage or rattling.
2. Temperature Test: Use a temperature gauge to measure the inlet and outlet temperatures. A significant difference (over 100°F) indicates a failing catalytic converter.
3. Replace Catalytic Converter (if necessary):
   • Remove the exhaust bolts securing the catalytic converter.
   • Disconnect any exhaust hangers and remove the converter.
   • Install the new catalytic converter, ensuring proper alignment and sealing.
   • Torque bolts to manufacturer specifications.

4. Reconnect Battery and Clear Codes

• Reconnect the battery and clear the error codes using the OBD-II scanner.
• Start the vehicle and let it idle to ensure there are no leaks.