my Honda Pilot Third Generation (2016-present) has a check engine light and code P0420

Solution

1. Preparation

• Gather all necessary tools and parts.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Allow the exhaust system to cool before working on it.

2. Inspect and Replace Oxygen Sensors

1. Remove the oxygen sensor (pre-catalytic converter):
   • Use an oxygen sensor socket to carefully unscrew the sensor.
   • Disconnect the wiring harness.
2. Install the new oxygen sensor:
   • Apply anti-seize compound to the threads of the new sensor.
   • Thread the new sensor in by hand, then tighten to the manufacturer's specifications (typically 30-35 ft-lbs).
   • Reconnect the wiring harness.
3. Repeat the process for the post-catalytic converter oxygen sensor if applicable.

3. Inspect and Replace Catalytic Converter (if necessary)

1. Remove the catalytic converter:
   • Support the exhaust system using jack stands if needed.
   • Unbolt the catalytic converter from the exhaust manifold and the mid-pipe using a socket wrench.
   • Carefully remove any heat shields if they obstruct access.
2. Install the new catalytic converter:
   • Position the new catalytic converter and align it with the exhaust manifold and mid-pipe.
   • Tighten bolts to the manufacturer's specifications (typically 30-35 ft-lbs).
   • Reattach any heat shields removed during disassembly.

4. Reset the Engine Control Module (ECM)

1. Reconnect the negative battery terminal.
2. Use the OBD-II scanner to clear the error codes.
3. Start the engine and allow it to reach operating temperature.