how to fix P0420 error code on Honda Accord 10th Generation (2018-2022)

Solution

1. Preparation

• Gather tools and necessary parts.
• Disconnect the negative battery terminal to ensure safety during repairs.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, ratchet, and torque wrench.
• Remove the upstream oxygen sensor.
• Inspect the sensor for damage or contamination.
• If faulty, replace it with a new OEM or high-quality aftermarket sensor.
• Torque the new sensor to the manufacturer’s specifications (typically around 30 ft-lbs).
• Repeat the process for the downstream oxygen sensor if needed.

3. Inspect and Replace Catalytic Converter

• Tools Required: Socket set, torque wrench, exhaust hangers tool, and penetrating oil.
• Locate the catalytic converter and visually inspect it for damage, rust, or holes.
• If the catalytic converter appears damaged or is clogged, remove it by loosening the bolts and exhaust hangers.
• Install the new catalytic converter, ensuring it fits securely and aligns with the exhaust system.
• Torque the bolts to the manufacturer’s specifications (typically varies, check manual).

4. Clear Codes and Test

• Reconnect the negative battery terminal.
• Use the OBD-II scanner to clear the P0420 code.
• Start the engine and allow it to reach operating temperature.
• Take the vehicle for a test drive to ensure the check engine light does not reappear.