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

Solution

1. Preparation

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

2. Inspect and Replace Oxygen Sensors

1. Locate the oxygen sensors: Identify the upstream (pre-catalytic converter) and downstream (post-catalytic converter) oxygen sensors.
2. Unplug the sensors: Carefully disconnect the electrical connectors from both sensors.
3. Remove the sensors: Use an oxygen sensor socket or wrench to unscrew the sensors from the exhaust.
4. Install new sensors: Apply anti-seize compound on the threads of the new sensors, then screw them into the exhaust. Tighten to the manufacturer's specifications (typically around 30-35 lb-ft).
5. Reconnect the electrical connectors: Ensure they click into place securely.

3. Inspect and Replace Catalytic Converter (if necessary)

1. Check for signs of damage: Inspect the catalytic converter for dents, cracks, or a honeycomb structure that is broken.
2. Remove the old catalytic converter: Unbolt the exhaust flange and any hangers securing the converter. Use a socket set to remove the bolts.
3. Install the new catalytic converter: Position the new converter in place, aligning it with the exhaust system. Secure it using the original hardware or new bolts if needed.
4. Torque the bolts: Tighten the bolts to the specified torque (typically around 40-50 lb-ft) to prevent leaks.

4. Clear Codes and Test

1. Reconnect the battery: Reattach the negative terminal and ensure all connections are secure.
2. Clear error codes: Use the OBD-II scanner to erase the P0420 code from the vehicle’s computer.
3. Test drive the vehicle: Drive for at least 20-30 miles to allow the ECU to re-evaluate the catalytic converter's efficiency.