how to fix P0420 code on Toyota Highlander XU70 (2020-Present)

Solution

1. Preparation

• Gather tools and parts required for repair.
• Disconnect the battery to ensure safety while working on electrical components.

2. Inspect and Replace Oxygen Sensors

1. Remove Upstream O2 Sensor:

   • Use an O2 sensor socket to carefully remove the upstream oxygen sensor from the exhaust manifold.
   • Inspect the sensor for damage or contamination.

2. Install New Upstream O2 Sensor:

   • Apply anti-seize compound to the threads of the new sensor.
   • Install the new upstream O2 sensor and torque to manufacturer's specifications (usually around 30 lb-ft).

3. Remove Downstream O2 Sensor:

   • Use the O2 sensor socket to remove the downstream oxygen sensor from the catalytic converter.
   • Check for any signs of damage to the sensor.

4. Install New Downstream O2 Sensor:

   • Apply anti-seize compound to the threads of the new sensor.
   • Install the new downstream O2 sensor and torque to manufacturer's specifications.

3. Inspect and Replace Catalytic Converter (if necessary)

1. Remove Exhaust Components:

   • Support the exhaust system with a jack stand.
   • Remove bolts or clamps securing the catalytic converter to the exhaust system using a socket set.

2. Install New Catalytic Converter:

   • Position the new catalytic converter in place.
   • Secure it using the original bolts or new hardware as recommended, tightening to the specified torque.

4. Reconnect Battery and Clear Codes

• Reconnect the battery terminals.
• Use an OBD-II scanner to clear the P0420 code from the ECM.

5. Test the Vehicle

• Start the engine and let it idle for a few minutes.
• Take the vehicle for a test drive to ensure that the check engine light does not reappear.