how to fix P0420 code on Toyota Highlander Third Generation (2014-2019)

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the negative battery terminal to avoid electrical shorts.

2. Inspect Exhaust System

• Tools Required: Visual inspection tools, flashlight
• Inspect the exhaust pipes, joints, and the catalytic converter for signs of rust, leaks, or physical damage. Repair any leaks found.

3. Test Oxygen Sensors

• Tools Required: OBD-II scanner, multimeter
• Reconnect the battery.
• Use an OBD-II scanner to monitor live data from the oxygen sensors while the engine is running.
• If the upstream sensor is not fluctuating between 0.1V and 0.9V, replace it.

4. Replace Oxygen Sensors (if necessary)

• Tools Required: Socket set, O2 sensor socket
• Unscrew the faulty oxygen sensor(s) from the exhaust system.
• Install the new oxygen sensor(s) and tighten them to the manufacturer's specifications.

5. Replace Catalytic Converter (if necessary)

• Tools Required: Socket set, jack and stands
• Raise the vehicle and support it securely.
• Disconnect the exhaust pipes from the catalytic converter.
• Remove the catalytic converter from its mounting brackets.
• Install the new catalytic converter and reconnect all exhaust components.
• Ensure all bolts are tightened to the manufacturer's torque specifications.