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

Solution

1. Preparation

• Tools Required: OBD-II scanner, multimeter, socket set, torque wrench, jack and jack stands.
• Safety Warnings: Disconnect the battery before working on electrical systems; ensure the vehicle is on a flat surface and securely supported by jack stands.

2. Inspect and Replace Oxygen Sensors

1. Locate the Oxygen Sensors:
   • The upstream sensor is typically located before the catalytic converter, while the downstream sensor is after it.
2. Remove the Oxygen Sensors:
   • Using the socket set, carefully unscrew the sensors from the exhaust pipe.
   • Be cautious of the sensor threads; use penetrating oil if they are stuck.
3. Install New Oxygen Sensors:
   • Apply anti-seize compound to the threads of the new sensors to prevent future seizing.
   • Hand-tighten the sensors first, then use the torque wrench to tighten to manufacturer specifications (usually around 30-50 Nm).

3. Inspect or Replace Catalytic Converter

1. Visual Inspection:
   • Check for any visible damage, rust, or rattling. If the converter is damaged or clogged, it will need replacement.
2. Remove and Replace the Catalytic Converter:
   • Disconnect the exhaust pipes from the catalytic converter using the socket set.
   • Remove any brackets or heat shields securing the converter.
   • Install the new catalytic converter, ensuring proper alignment with the exhaust system.
   • Reconnect all bolts and tighten to the manufacturer’s torque specifications.

4. Clear Error Codes

1. Reconnect the Battery:
   • Reconnect the negative terminal of the battery.
2. Use the OBD-II Scanner:
   • Clear the P0420 code and any other related codes from the engine control module.

5. Test the Vehicle

1. Perform a Test Drive:
   • Drive the vehicle for a short distance to monitor for any reoccurrence of the check engine light and ensure the issue is resolved.