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

Solution

1. Preparation

• Gather tools and parts.
• Ensure the vehicle is parked on a level surface and the engine is off.
• Disconnect the battery to avoid electrical shorts.

2. Inspect and Replace Oxygen Sensors

1. Disconnect the oxygen sensor connectors: Locate the upstream and downstream oxygen sensors and disconnect their electrical connectors.
2. Remove the sensors: Use an oxygen sensor socket to carefully unscrew the sensors from the exhaust pipes.
3. Install new sensors: Apply anti-seize compound to the threads of the new oxygen sensors and install them in reverse order of removal. Torque to manufacturer's specifications (usually around 30 ft-lbs).
4. Reconnect electrical connectors: Ensure the connectors are securely attached to the new sensors.

3. Inspect and Replace the Catalytic Converter (if necessary)

1. Support the vehicle: Raise it on jack stands and ensure it is stable.
2. Remove the exhaust system components: Depending on the design, unbolt the exhaust pipes connected to the catalytic converter and any heat shields.
3. Remove the catalytic converter: Unscrew the bolts securing it to the exhaust manifold and the downstream pipe. Carefully take it out.
4. Install the new catalytic converter: Position the new catalytic converter and secure it with appropriate bolts. Ensure a proper seal with new gaskets if required.
5. Reattach exhaust components: Reinstall any sections of the exhaust system that were removed, tightening bolts to manufacturer specifications.

4. Reset the Engine Control Module (ECM)

1. Reconnect the battery: Reconnect the negative battery terminal.
2. Clear the trouble codes: Use an OBD-II scanner to clear the P0420 code from the ECM.
3. Test drive the vehicle: Drive for a short distance to allow the ECM to monitor the new components and check for any reoccurring codes.