how to fix P0420 in Honda Accord 10th Generation (2018-2022)

Solution

1. Preparation

• Gather necessary tools and parts, including an OBD-II scanner, multimeter, socket set, and safety gear.
• Ensure the vehicle is parked on a level surface, and the engine is cool.
• Disconnect the battery to prevent electrical shorts.

2. Inspect and Replace Oxygen Sensors

1. Remove the old oxygen sensors:

   • Locate the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
   • Use a socket wrench to unscrew and remove both sensors.
   • Ensure to note the placement of each sensor for proper reinstallation.

2. Install new oxygen sensors:

   • Apply anti-seize compound to the threads of the new sensors.
   • Install the upstream sensor first, followed by the downstream sensor, ensuring they are tightened to the manufacturer’s torque specifications (usually around 30 Nm or 22 lb-ft).

3. Inspect and Replace the Catalytic Converter

1. Remove the catalytic converter:

   • Remove the bolts or clamps securing the catalytic converter to the exhaust system using a socket set.
   • Carefully lower the catalytic converter from the vehicle.

2. Install the new catalytic converter:

   • Position the new catalytic converter in place and secure it using the original bolts or clamps.
   • Ensure all connections are tight to prevent exhaust leaks.

4. Reconnect Battery and Clear Codes

1. Reconnect the battery:

   • Reattach the battery terminals, starting with the positive terminal followed by the negative terminal.

2. Clear the OBD-II codes:

   • Use an OBD-II scanner to clear the P0420 code from the vehicle’s computer.

5. Test Drive

1. Perform a test drive:
   • Drive the vehicle under various conditions to allow the computer to monitor the catalytic converter’s efficiency.
   • Monitor the vehicle's performance and check for any reoccurrence of the check engine light.