how to fix P0420 code on my Honda CR-V Sixth Generation (2023-present)

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the negative terminal of the battery to prevent electrical shorts.
• Allow the vehicle to cool down if it has been running.

2. Inspect Oxygen Sensors

• Tools Required: OBD-II scanner, multimeter.
• Remove the upstream (pre-catalytic) oxygen sensor using a socket wrench.
• Test the oxygen sensor with a multimeter:
  • Set the multimeter to the voltage setting.
  • Start the engine and observe the voltage readings; it should fluctuate between 0.1V to 0.9V.
• If the readings are out of this range, replace the oxygen sensor.
• Reinstall the sensor if it is functioning properly.

3. Check Catalytic Converter

• Tools Required: Socket set, possibly a pry bar.
• Inspect the catalytic converter for any physical damage or rattling sounds indicating internal failure.
• If damaged, remove the catalytic converter by unbolting it from the exhaust system.
• Replace it with an OEM or high-quality aftermarket catalytic converter, ensuring proper fitment.

4. Repair Exhaust Leaks

• Tools Required: Exhaust sealant, clamps, or welding tools.
• Inspect all joints and connections in the exhaust system.
• Use exhaust sealant to repair small leaks or replace components as necessary.
• Ensure all connections are tight and secure.

5. Reassemble and Reset

• Reinstall any components that were removed for inspection or repair.
• Reconnect the battery terminal.
• Use the OBD-II scanner to clear the P0420 code from the ECU.