Honda Accord 8th Generation (2008-2012) check engine light and code P0420 how to fix

Solution

1. Preparation

• Gather tools and parts required for the repair.
• Disconnect the negative battery terminal to avoid electrical shorts.
• Allow the engine to cool down completely before working on the exhaust system.

2. Inspect and Replace Oxygen Sensors (if faulty)

1. Locate the upstream (pre-cat) and downstream (post-cat) oxygen sensors.
2. Use a wrench to remove the oxygen sensors from their respective locations.
3. Inspect the sensor wiring for damage or corrosion.
4. If faulty, install new oxygen sensors, ensuring they are properly torqued to manufacturer specifications (usually around 30-40 ft-lbs).
5. Reconnect the electrical connectors securely.

3. Inspect and Replace Catalytic Converter (if necessary)

1. If the catalytic converter is damaged or blocked, use a socket set to remove the exhaust pipes connected to the converter.
2. Carefully detach the catalytic converter from the exhaust system.
3. Install the new catalytic converter, ensuring proper alignment and fit.
4. Torque the exhaust bolts to manufacturer specifications (typically between 25-30 ft-lbs).
5. Reconnect any heat shields or brackets that were removed.

4. Reset Engine Light

1. Reconnect the negative battery terminal.
2. Use the OBD-II scanner to clear the P0420 code from the vehicle’s computer.
3. Start the engine and allow it to reach operating temperature.