my Toyota Highlander has a check engine light and code P0420 what does that mean

Solution

1. Preparation

• Tools Required: OBD-II scanner, socket set, jack and jack stands, safety goggles, gloves.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Raise the vehicle using a jack and secure it on jack stands.

2. Inspect and Replace Oxygen Sensors

1. Locate the oxygen sensors: Identify the upstream (pre-catalytic converter) and downstream (post-catalytic converter) O2 sensors.
2. Remove the sensors:
   • Use a socket to unscrew the O2 sensors from the exhaust pipes.
   • Disconnect the electrical connectors from the sensors.
3. Install new sensors:
   • Apply anti-seize compound to the threads of the new sensors.
   • Install the new sensors and reconnect the electrical connectors.
   • Torque the sensors to the manufacturer's specifications (usually around 30 lb-ft).

3. Inspect and Replace Catalytic Converter (if needed)

1. Visual inspection: Check for any physical damage or signs of clogging in the catalytic converter.
2. Remove the catalytic converter:
   • Loosen and remove the exhaust bolts connecting the converter to the exhaust system.
   • Use a saw or cutter if the converter is welded.
3. Install new catalytic converter:
   • Position the new catalytic converter into place.
   • Secure it with bolts and torque to the manufacturer's specifications.
   • Ensure all gaskets are replaced to prevent exhaust leaks.

4. Clear Codes and Test Drive

1. Reconnect the negative battery terminal.
2. Use the OBD-II scanner to clear the P0420 code.
3. Start the engine and perform a test drive to ensure the check engine light remains off and the vehicle operates normally.