how to fix P0420 code on Honda Accord 9th Generation (2013-2017)

Solution

1. Preparation

• Gather tools and parts: OBD-II scanner, multimeter, socket set, torque wrench, replacement O2 sensors (if needed), and a new catalytic converter (if needed).
• Disconnect the battery to avoid electrical shorts during repairs.

2. Inspect and Test O2 Sensors

• Sub-step 1: Locate the upstream and downstream O2 sensors on the exhaust system.
• Sub-step 2: Remove the electrical connectors from both O2 sensors.
• Sub-step 3: Using a multimeter, set it to measure voltage and connect it to the sensor terminals.
• Sub-step 4: Start the engine and observe the voltage readings. The upstream sensor should fluctuate between 0.1 to 0.9 volts. The downstream sensor should have a steadier reading. If readings are outside these ranges, consider replacing the faulty sensor.

3. Replace O2 Sensors (if needed)

• Sub-step 1: Use a socket wrench to remove the faulty O2 sensor from the exhaust.
• Sub-step 2: Apply anti-seize compound on the threads of the new sensor to prevent future seizing.
• Sub-step 3: Install the new O2 sensor and torque it to the manufacturer's specifications (typically around 30 lb-ft).
• Sub-step 4: Reconnect the electrical connector.

4. Inspect and Replace Catalytic Converter (if needed)

• Sub-step 1: Check for any physical damage or excessive rattling from the catalytic converter.
• Sub-step 2: If replacement is needed, remove the exhaust bolts securing the catalytic converter to the exhaust manifold and the exhaust pipe.
• Sub-step 3: Install the new catalytic converter, ensuring proper alignment.
• Sub-step 4: Torque all bolts to the manufacturer's specifications (typically around 40 lb-ft).
• Sub-step 5: Reconnect any hangers or brackets holding the exhaust system in place.

5. Final Checks

• Sub-step 1: Reconnect the battery.
• Sub-step 2: Clear the error codes using an OBD-II scanner.
• Sub-step 3: Start the engine and let it run for a few minutes to check for exhaust leaks.
• Sub-step 4: Take the vehicle for a test drive and monitor for any reoccurrence of the check engine light.