how to troubleshoot the check engine light and P0420 in my Honda Accord 9th Generation (2013-2017)?

Solution

1. Preparation

• Gather tools and materials needed for the repair.
• Tools Required: OBD-II scanner, multimeter, socket set, torque wrench, jack and jack stands, safety goggles.
• Safety Warnings: Disconnect the battery before working on electrical systems.

2. Inspect and Test Oxygen Sensors

1. Locate the oxygen sensors: Identify the pre-catalytic (upstream) and post-catalytic (downstream) oxygen sensors.
2. Disconnect the sensors: Carefully unplug the connectors from both sensors.
3. Test the sensors: Use a multimeter to check the voltage output of the pre-cat sensor (should fluctuate between 0.1V to 0.9V). The post-cat sensor should show a more stable voltage (around 0.5V).
4. Replace faulty sensors: If either sensor fails the test, replace with OEM or quality aftermarket parts.

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

1. Check for physical damage: Look for dents, cracks, or signs of overheating on the catalytic converter.
2. Remove the catalytic converter:
   • Raise the vehicle and secure it with jack stands.
   • Remove any heat shields and exhaust bolts using a socket set.
3. Inspect the internals: Look for signs of clogging or melting of the catalyst material.
4. Install a new catalytic converter:
   • Place the new converter in position and hand-tighten the bolts.
   • Torque the bolts to the manufacturer's specifications (usually specified in the service manual).
5. Reinstall any heat shields and ensure all connections are secure.