my Toyota Corolla E170 (2013-2019) has a check engine light on with code P0420, what does it mean

Solution

1. Preparation

• Gather tools: OBD-II scanner, multimeter, socket set, jack and jack stands, safety goggles, and gloves.
• Ensure the vehicle is parked on a flat surface, and the engine is cool.

2. Inspect and Replace Oxygen Sensors

1. Locate the oxygen sensors: Identify the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
2. Disconnect electrical connectors: Carefully unplug the connectors from the oxygen sensors.
3. Remove oxygen sensors: Use the appropriate socket to remove the sensors from their respective locations.
4. Install new sensors: Apply anti-seize compound on the threads of the new oxygen sensors, install them, and torque to manufacturer specifications (typically around 30 lb-ft).
5. Reconnect electrical connectors: Ensure connections are secure.

3. Inspect Catalytic Converter

1. Check for blockages: Use a vacuum gauge to test for back pressure at the exhaust pipe before the catalytic converter. A reading above 2.5 psi may indicate blockage.
2. Inspect for physical damage: Examine the catalytic converter for dents, cracks, or signs of overheating (e.g., discoloration).
3. Replace if necessary: If damage or blockage is found, remove the old catalytic converter by unbolting it from the exhaust system and install a new unit following manufacturer specifications.

4. Clear Codes and Test Drive

1. Clear DTCs: Use the OBD-II scanner to erase the P0420 code from the vehicle's computer.
2. Test drive the vehicle: Drive the car for at least 30 minutes under various conditions to ensure the check engine light does not reappear.