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

Solution

1. Preparation

• Tools Required: OBD-II scanner, socket set, multimeter, torque wrench, jack and jack stands, safety goggles, gloves.
• Ensure the vehicle is on a level surface and the engine is cool.
• Disconnect the battery to prevent any electrical issues.

2. Inspect Exhaust System

• Sub-steps:
  • Raise the vehicle securely using a jack and jack stands.
  • Visually inspect the exhaust system from the engine manifold to the tailpipe for any leaks or damage.
  • Check for loose or broken bolts on the exhaust flanges.

3. Test Oxygen Sensors

• Sub-steps:
  • Locate the upstream and downstream oxygen sensors on the exhaust system.
  • Disconnect the sensor connectors and use a multimeter to check the voltage output.
  • Replace any oxygen sensors that are not within the normal voltage range (typically between 0.1V to 0.9V for upstream).

4. Replace Catalytic Converter (if necessary)

• Sub-steps:
  • If the catalytic converter is damaged or clogged, remove it by unscrewing the bolts connecting it to the exhaust system.
  • Install the new catalytic converter, ensuring proper alignment and fitment.
  • Torque the bolts to manufacturer specifications (usually around 30-50 ft-lbs, but check service manual for exact values).

5. Reset the ECM

• Sub-steps:
  • Reconnect the battery terminals.
  • Use an OBD-II scanner to clear the P0420 code from the ECM.
  • Start the engine and allow it to reach operating temperature.