why is my Toyota Camry Seventh Generation (2012-2017) check engine light on with code P0420

Solution

1. Preparation

• Gather tools and parts necessary for the repair.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Allow the vehicle to cool if the engine has been running.

2. Inspect and Replace Oxygen Sensors

1. Locate the oxygen sensors:
   • The upstream sensor is typically located in the exhaust manifold or just before the catalytic converter, while the downstream sensor is located after the catalytic converter.
2. Remove the oxygen sensors:
   • Use an O2 sensor socket or wrench to carefully unscrew the sensors from their respective ports.
   • Ensure to note the orientation for correct installation.
3. Install new sensors:
   • Apply anti-seize compound to the threads of the new sensors to prevent seizing.
   • Screw in the new sensors by hand, then tighten them to manufacturer specifications (usually around 30 Nm or as specified).

3. Check and Replace Catalytic Converter (if necessary)

1. Inspect the catalytic converter:
   • Look for signs of physical damage, such as dents or rust, and check for any clogs by tapping it gently (it should sound hollow).
2. Remove the catalytic converter:
   • Loosen and remove the bolts connecting the catalytic converter to the exhaust pipe and exhaust manifold.
   • Carefully remove the catalytic converter from the vehicle.
3. Install a new catalytic converter:
   • Position the new catalytic converter in place and connect it to the exhaust system.
   • Secure with new gaskets and bolts, ensuring they are tightened to the specified torque.

4. Reset the Engine Control Unit (ECU)

1. Reconnect the battery:
   • Reattach the negative terminal to the battery.
2. Clear the codes:
   • Use the OBD-II scanner to clear the P0420 code from the system.
3. Start the vehicle and allow it to reach operating temperature.