how to fix P0420 code on Honda Accord Eleventh Generation (2023-present)

Solution

1. Preparation

• Tools Required: OBD-II scanner, multimeter, socket set, jack and jack stands, safety goggles, gloves.
• Ensure the vehicle is parked on a level surface and is in park (or neutral for manual transmissions).
• Disconnect the battery to prevent electrical shorts.

2. Inspect and Replace Oxygen Sensors

1. Locate the oxygen sensors:
   • The upstream sensor is typically located before the catalytic converter, and the downstream sensor is after it.
2. Remove the oxygen sensors:
   • Use a socket wrench to unscrew the sensors from their respective locations.
3. Install new oxygen sensors:
   • Apply anti-seize compound to the threads of the new sensors.
   • Screw the new sensors into place and tighten them to the manufacturer's specified torque (usually around 30 lb-ft).
4. Reconnect the battery.

3. Inspect and Replace the Catalytic Converter

1. Remove the exhaust components:
   • Use a socket set to unbolt the catalytic converter from the exhaust system.
   • Ensure you have a container to catch any residual fluids.
2. Inspect the old catalytic converter:
   • Check for physical damage, blockage, or contamination.
3. Install the new catalytic converter:
   • Place the new catalytic converter into position and secure it with bolts.
   • Tighten to the manufacturer's specifications (typically 30 lb-ft).
4. Reattach any exhaust components previously removed.

4. Clear Codes and Test

1. Reset the OBD-II system:
   • Use the OBD-II scanner to clear the P0420 trouble code.
2. Conduct a test drive:
   • Drive the vehicle under various conditions to ensure the check engine light does not reappear and to verify performance.