how to fix Honda Pilot Third Generation (2016-present) P0420 catalyst efficiency code

Solution

1. Preparation

• Gather tools and parts.
• Disconnect the negative battery terminal to prevent electrical shock.
• Allow the vehicle to cool down before proceeding to work on the exhaust system.

2. Inspecting Oxygen Sensors

• Tools Required: OBD-II scanner, multimeter
• Remove the upstream (pre-catalytic converter) oxygen sensor using a socket wrench.
• Connect the multimeter to the sensor wires to check voltage output; it should fluctuate between 0.1 to 0.9 volts.
• If the sensor is faulty, replace it with a new one. Reinstall and reconnect.

3. Inspecting and Testing the Catalytic Converter

• Tools Required: Jack and jack stands, socket set, exhaust pipe cutter (if needed)
• Elevate the vehicle using a jack and secure it with jack stands.
• Visually inspect the catalytic converter for any signs of damage or blockage.
• If physical damage is found, proceed to remove the catalytic converter. Use a socket set to loosen the bolts connecting it to the exhaust.
• If no damage is visible, perform a catalytic converter efficiency test. This may involve checking the temperature before and after the converter; the exit temperature should be significantly higher than the entrance temperature.
• If the catalytic converter fails the efficiency test, replace it.

4. Reassemble and Reconnect

• Reinstall any removed components, ensuring all bolts are torqued to manufacturer specifications.
• Reconnect the negative battery terminal.
• Clear the error codes using the OBD-II scanner.