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

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the battery negative terminal to ensure safety.
• Raise the vehicle using a jack and secure it with jack stands.

2. Inspect and Test Oxygen Sensors

• Tools Required: OBD-II scanner, multimeter.
• Remove the upstream (pre-catalytic) oxygen sensor using a socket wrench.
• Use a multimeter to test the voltage output of the upstream sensor while the engine is running; it should fluctuate between 0.1V and 0.9V.
• Repeat the process for the downstream (post-catalytic) oxygen sensor.
• If either sensor is faulty, replace it.

3. Inspect Catalytic Converter

• Tools Required: Socket set, torque wrench.
• Visually inspect the catalytic converter for any dents, cracks, or signs of blockage.
• If blockage or damage is observed, replace the catalytic converter.
• Ensure all connections are tight and secure.

4. Clear Codes and Test Drive

• Reconnect the battery terminal.
• Use the OBD-II scanner to clear the P0420 code.
• Perform a test drive for approximately 20 minutes to allow the vehicle to enter closed-loop operation.