why does my Honda Pilot YF4 (2023-Present) have a P0420 code after new cat?

Solution

1. Preparation

• Gather tools and parts.
• Disconnect the battery to prevent electrical shorts.
• Ensure the vehicle is on a flat surface and securely raised if needed.

2. Inspect Oxygen Sensors

1. Locate the upstream and downstream oxygen sensors.
2. Disconnect the wiring harness from both sensors.
3. Test the voltage output of the upstream oxygen sensor while the engine is running; it should fluctuate between 0.1V and 0.9V.
4. Test the downstream oxygen sensor; it should produce a stable voltage if the catalytic converter is functioning properly.
   • Tools Required: Multimeter

3. Inspect Exhaust System

1. Visually check the exhaust system for any leaks, particularly around joints and connections.
2. Use a smoke machine to check for leaks if necessary.
3. Repair any identified leaks using exhaust sealant or replace damaged components as needed.
   • Tools Required: Smoke machine, exhaust sealant

4. Recheck Catalytic Converter Installation

1. Ensure the new catalytic converter is properly installed without any obstructions.
2. Verify that all exhaust clamps and bolts are tightened to manufacturer specifications.
3. Replace any damaged gaskets or seals that may cause leaks.
   • Tools Required: Socket set, torque wrench

5. Clear Codes and Test Drive

1. Use the OBD-II scanner to clear the P0420 code.
2. Conduct a test drive under various conditions (idle, acceleration, highway) to ensure the issue is resolved.
   • Tools Required: OBD-II scanner