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

Solution

1. Preparation

• Tools Required: OBD-II scanner, socket set, torque wrench, infrared thermometer, multimeter, exhaust pipe cutter (if necessary), jack and jack stands.
• Disconnect the negative battery terminal to prevent electrical shorts.

2. Inspect and Replace Oxygen Sensors

1. Locate the oxygen sensors: Identify the upstream (pre-catalytic converter) and downstream (post-catalytic converter) sensors.
2. Remove the upstream sensor: Use a socket or wrench to carefully unscrew the sensor.
3. Install the new upstream sensor: Apply anti-seize compound to the threads of the new sensor, then screw it into place and tighten to manufacturer torque specifications (usually around 30-40 ft-lbs).
4. Repeat for the downstream sensor: Follow the same procedure as outlined for the upstream sensor.

3. Inspect and Replace Catalytic Converter (if necessary)

1. Check the catalytic converter: If the previous steps did not resolve the P0420 code, inspect the catalytic converter for damage or blockage.
2. Remove the catalytic converter: Use a socket set to unbolt the catalytic converter from the exhaust system. If necessary, use an exhaust pipe cutter to separate.
3. Install the new catalytic converter: Position the new converter in place, then secure it using the bolts. Ensure all gaskets are in good condition or replace them as needed.
4. Torque the bolts: Follow the manufacturer’s specifications for proper torque settings.

4. Reconnect Battery and Clear Codes

1. Reconnect the negative battery terminal.
2. Use the OBD-II scanner to clear the P0420 code from the vehicle’s computer.