why is my Toyota Corolla E170 (2013-2019) check engine light on with code P0420

Solution

1. Preparation

• Gather tools and safety gear (gloves, goggles).
• Ensure the vehicle is parked on a level surface and the engine is off.
• Disconnect the battery to prevent any electrical issues during the repair.

2. Inspect and Replace Oxygen Sensors (if necessary)

• Remove the upstream oxygen sensor using an O2 sensor socket.
• Inspect the connector and wiring for damage; replace if necessary.
• Install the new upstream oxygen sensor and torque to the manufacturer's specifications (typically 30-50 ft-lbs).
• Repeat the process for the downstream oxygen sensor if it was found faulty.

3. Inspect and Replace Catalytic Converter (if necessary)

• If the catalytic converter is damaged, support the vehicle on jack stands.
• Remove the bolts securing the catalytic converter to the exhaust system using a socket wrench.
• Carefully disconnect the exhaust hangers and remove the catalytic converter.
• Install the new catalytic converter, ensuring proper alignment with the exhaust system.
• Torque the bolts to the manufacturer's specifications (usually between 25-35 ft-lbs).

4. Reconnect Battery and Clear Codes

• Reconnect the battery terminals.
• Use an OBD-II scanner to clear the P0420 code from the ECU.
• Start the engine and let it idle for a few minutes.