how to fix the P0420 catalytic converter code in Toyota Highlander Fourth Generation (2020-present)

Solution

1. Preparation

• Gather tools and parts needed for the repair.
• Ensure the vehicle is parked on a level surface, and the engine is cool.
• Disconnect the battery to prevent electrical shorts.

2. Inspect and Replace Oxygen Sensors

1. Locate the Oxygen Sensors:
   • The upstream sensor is located before the catalytic converter; the downstream sensor is after it.
2. Remove the Sensors:
   • Using an O2 sensor socket, carefully unscrew the sensors from their respective locations.
3. Check Sensor Function:
   • Test the sensors with a multimeter for proper voltage output. Replace any faulty sensors.
4. Install New Sensors:
   • Apply anti-seize compound to the threads of the new sensors.
   • Install them in the same orientation as the old sensors and torque them to the manufacturer's specifications (usually 30-50 lb-ft).

3. Check and Replace the Catalytic Converter

1. Inspect the Catalytic Converter:
   • Look for any signs of physical damage, such as dents or rust.
2. Remove the Catalytic Converter:
   • Unbolt the exhaust flanges and any brackets holding the catalytic converter in place.
   • Carefully remove the converter from the exhaust system.
3. Install New Catalytic Converter:
   • Position the new catalytic converter in place and secure it with bolts.
   • Torque the bolts to the manufacturer's specifications (typically around 40-60 lb-ft).
4. Reconnect the Exhaust System:
   • Ensure all connections are tight and seal any leaks with exhaust sealant if necessary.

4. Reconnect Battery and Clear Codes

1. Reconnect the Battery:
   • Ensure all connections are secure and reattach the negative battery terminal.
2. Clear the Check Engine Light:
   • Use the OBD-II scanner to clear the P0420 code from the vehicle's computer.