how to fix the P0420 code on my Toyota Corolla E170 (2013-2019)

Solution

1. Preparation

• Gather tools and parts required.
• Ensure the vehicle is parked on a level surface and the engine is off.
• Disconnect the negative battery terminal to reset the ECU.

2. Inspect and Replace Oxygen Sensors

1. Locate the upstream (pre-catalytic converter) and downstream (post-catalytic converter) oxygen sensors.
2. Use a socket wrench to carefully remove the upstream oxygen sensor.
3. Inspect the sensor for damage or contamination and replace it if necessary.
4. Repeat the process for the downstream oxygen sensor.
5. Reconnect both oxygen sensors securely.

3. Inspect and Replace Catalytic Converter

1. Raise the vehicle using jack stands and remove the exhaust heat shield if applicable.
2. Unbolt the catalytic converter from the exhaust manifold and the exhaust pipe using a socket set.
3. Inspect the catalytic converter for internal damage or clogging (look for rattling or discoloration).
4. Install the new catalytic converter, ensuring proper alignment.
5. Torque the bolts to manufacturer specifications (typically around 30-40 ft-lbs, but verify with a service manual).
6. Reattach the heat shield if removed.

4. Reset the ECU

1. Reconnect the negative battery terminal.
2. Start the vehicle and allow it to reach operating temperature.
3. Disconnect the battery again for a few minutes to clear the P0420 code from the ECU.

5. Test Drive

1. Take the vehicle for a test drive under various driving conditions.
2. Monitor for any reappearance of the check engine light.