what does it mean if my Toyota Highlander is showing a P0420 code?

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the vehicle is parked on a level surface and the engine is cool.
• Disconnect the battery to prevent any electrical shorts.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, wrench set, multimeter, safety glasses.
• Remove the upstream oxygen sensor by unscrewing it from the exhaust manifold.
• Use the multimeter to test the sensor; if it’s outside of specification, replace it.
• Install the new sensor and reconnect the electrical connector.

3. Inspect and Replace the Catalytic Converter

• Tools Required: Socket set, jack stands, exhaust pipe cutter, replacement catalytic converter, gasket material.
• Raise the vehicle and secure it with jack stands.
• Disconnect the exhaust pipes leading to and from the catalytic converter using a socket set.
• Remove the old catalytic converter, checking for any damage.
• Install the new catalytic converter, ensuring all gaskets are in place and secure all bolts to the manufacturer's torque specifications.

4. Clear Codes and Test Drive

• Reconnect the battery and use the OBD-II scanner to clear the P0420 code.
• Start the engine and let it idle for a few minutes before performing a test drive to ensure the check engine light does not reappear.