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

Solution

1. Preparation

• Gather tools and parts for the repair.
• Ensure the vehicle is parked on a level surface, and the engine is cool.
• Disconnect the negative battery terminal to prevent electrical shorts.

2. Inspect and Replace Oxygen Sensors

1. Locate the Oxygen Sensors:

   • Identify the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.

2. Remove the Oxygen Sensors:

   • Use an oxygen sensor socket to carefully unscrew the sensors from their respective locations.

3. Inspect Sensors:

   • Check for signs of carbon buildup or damage on the sensors.

4. Replace if Necessary:

   • If faulty, install new oxygen sensors by screwing them in place and torquing to the manufacturer’s specifications (usually around 30 ft-lbs).

3. Inspect and Replace Catalytic Converter (if necessary)

1. Inspect the Catalytic Converter:

   • Look for any signs of damage, such as dents, cracks, or a rattling noise indicating internal damage.

2. Remove the Catalytic Converter:

   • Loosen and remove the bolts securing the catalytic converter to the exhaust pipes using a socket set.
   • Carefully take out the catalytic converter from the exhaust system.

3. Install New Catalytic Converter:

   • Position the new catalytic converter in place, ensuring proper alignment.
   • Secure it with new gaskets and bolts, torquing to manufacturer specifications (typically around 30 ft-lbs).

4. Clear Codes and Test Drive

1. Reconnect the Battery:

   • Reconnect the negative battery terminal.

2. Clear the Error Codes:

   • Use an OBD-II scanner to erase the P0420 code and any other related codes.

3. Test Drive:

   • Drive the vehicle for around 20-30 minutes to ensure the system monitors operate correctly and verify that the check engine light does not reappear.