how to fix P0420 code on Honda Accord Eleventh Generation (2023-present)

Solution

1. Preparation

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

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 Sensors: Use the appropriate socket to unscrew the sensors carefully. Disconnect the wiring harness from each sensor.
3. Test the Sensors: Use a multimeter to test the resistance and voltage output of each sensor according to manufacturer specifications.
4. Replace Faulty Sensors: If any sensor is found defective, replace it with a new one. Torque the new sensors to the specification (usually around 30 lb-ft).

3. Inspect and Replace the Catalytic Converter

1. Remove Exhaust Components: If the catalytic converter is suspected to be faulty, remove any components obstructing access (heat shields, exhaust pipes).
2. Unbolt the Catalytic Converter: Use a socket set to unbolt the catalytic converter from the exhaust manifold and exhaust pipe.
3. Inspect the Catalytic Converter: Check for physical damage, excessive rattling, or clogged passages.
4. Install New Catalytic Converter: If replacement is necessary, install the new catalytic converter, ensuring the gaskets are in good condition. Torque to specification.
5. Reassemble Exhaust Components: Reattach any exhaust components removed earlier, ensuring all bolts are tightened to specification.

4. Reset the Engine Control Module (ECM)

1. Reconnect the Battery: Reconnect the negative battery terminal.
2. Clear the Codes: Use the OBD-II scanner to clear the P0420 code from the ECM.
3. Test Drive: Take the vehicle for a test drive to ensure everything is functioning properly.