how to fix P0420 code on Honda Accord 9th Generation (2013-2017)

Solution

1. Preparation

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

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 and remove the sensors.
   • Note the orientation for reinstallation.

3. Install New Oxygen Sensors

   • Apply anti-seize compound to the threads of the new sensors.
   • Install the new sensors and torque them to manufacturer specifications (typically around 30 ft-lbs).

3. Inspect and Replace Catalytic Converter (if necessary)

1. Inspect Catalytic Converter

   • Check for physical damage, rattling sounds, or excessive heat.
   • If damaged, proceed with replacement.

2. Remove the Old Catalytic Converter

   • Use a socket set to unbolt the catalytic converter from the exhaust system.
   • Carefully remove any heat shields and gaskets.

3. Install New Catalytic Converter

   • Position the new catalytic converter in place.
   • Use new gaskets and bolts, tightening to the manufacturer’s torque specifications (typically around 30-35 ft-lbs).

4. Reset the Check Engine Light

• Reconnect the negative battery terminal.
• Use the OBD-II scanner to clear the P0420 code.

5. Test the System

• Start the engine and allow it to reach operating temperature.
• Perform a test drive to ensure the check engine light remains off.