how to fix P0420 code on Toyota Highlander Fourth Generation (2020-present)

Solution

1. Preparation

• Tools Required: OBD-II scanner, multimeter, socket set, jack and jack stands, safety glasses, gloves.
• Disconnect the battery to ensure safety while working on electrical components.
• Allow the engine to cool before working on the exhaust system.

2. Inspect Exhaust System

• Raise the vehicle using a jack and secure it on jack stands.
• Visually inspect the exhaust pipes, joints, and the catalytic converter for any signs of damage or leaks.
• Tighten any loose connections and replace damaged sections.

3. Test Oxygen Sensors

• Locate the upstream (pre-catalytic converter) and downstream (post-catalytic converter) oxygen sensors.
• Disconnect the sensors and use a multimeter to check the voltage output:
  • Upstream: should fluctuate between 0.1 to 0.9 volts.
  • Downstream: should remain stable (around 0.5 volts) if the catalytic converter is functioning correctly.
• Replace any faulty sensors.

4. Replace Catalytic Converter (if necessary)

• If the catalytic converter is damaged or blocked, it will need replacement:
  • Remove the exhaust system components connected to the catalytic converter using the socket set.
  • Disconnect any heat shields or additional brackets.
  • Install the new catalytic converter, ensuring all gaskets are replaced.
  • Torque all bolts to the manufacturer's specifications (typically 25-30 lb-ft).

5. Reconnect Battery and Clear Codes

• Reconnect the battery terminals.
• Use the OBD-II scanner to clear the P0420 code.
• Start the vehicle and allow it to reach operating temperature.