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

Solution

1. Preparation

• Gather all necessary tools and parts.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Ensure the vehicle is on a flat surface and securely supported with jack stands if necessary.

2. Inspect and Test Oxygen Sensors

• Tools Required: OBD-II scanner, multimeter
• Remove the upstream (pre-catalytic) oxygen sensor by disconnecting its electrical connector and using a socket wrench.
• Inspect the sensor for damage; if faulty, replace it with a new OEM sensor.
• Connect the multimeter to the sensor to check its voltage output while the engine is running. Ensure the readings fluctuate between 0.1 and 0.9 volts.

3. Inspect Catalytic Converter

• Tools Required: Infrared thermometer
• Use the infrared thermometer to measure the temperature before and after the catalytic converter. A difference of more than 100 degrees Fahrenheit indicates a failing catalytic converter.
• If the converter is damaged or clogged, proceed to replace it.

4. Replace Catalytic Converter (if necessary)

• Tools Required: Socket set, exhaust gasket, torque wrench
• Remove the exhaust bolts connecting the catalytic converter to the exhaust manifold and the exhaust pipe.
• If there are any gaskets, replace them as well.
• Install the new catalytic converter, ensuring it is aligned properly with the exhaust system.
• Torque the bolts to the manufacturer’s specifications (refer to the service manual for exact torque values).

5. Reconnect Battery and Clear Codes

• Reconnect the negative battery terminal.
• Use the OBD-II scanner to clear the P0420 code from the system.