what does it mean if my Honda Pilot is showing code P0420

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the battery to prevent electrical shorts.
• Allow the engine to cool down before starting any work on the exhaust system.

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. Remove the Sensors: Use an oxygen sensor socket to carefully unscrew the sensors from their respective locations.
   • Tools Required: Oxygen sensor socket, ratchet.
3. Inspect the Sensors: Examine the sensors for carbon buildup or damage. Replace if necessary.
4. Install New Sensors: Apply anti-seize compound to the threads of the new sensors and install them securely.
   • Torque specifications: Typically 30-40 ft-lbs, check manufacturer specifications.

3. Examine and Replace the Catalytic Converter

1. Remove the Exhaust System Components: If necessary, unbolt and remove components of the exhaust system to access the catalytic converter.
   • Tools Required: Socket set, exhaust hanger removal tool.
2. Inspect the Catalytic Converter: Look for signs of damage, such as dents, rust, or physical blockages.
3. Replace the Catalytic Converter: If damaged, remove the old catalytic converter by unbolting it from the exhaust pipes and installing a new one.
   • Ensure proper alignment and secure all bolts to the recommended torque specifications.

4. Clear the Codes and Test Drive

1. Reconnect the Battery: Once repairs are complete, reconnect the battery.
2. Clear the OBD-II Codes: Use an OBD-II scanner to reset the check engine light.
3. Test Drive the Vehicle: Take the vehicle for a test drive to ensure it operates normally and that the check engine light does not reappear.