how to fix P0420 code on Toyota Highlander Fourth Generation (2020-present)

Solution

1. Preparation

• Gather tools: OBD-II scanner, multimeter, socket set, torque wrench, and safety glasses.
• Park the vehicle on a flat surface and ensure the engine is cool. Disconnect the battery.

2. Inspect and Replace Oxygen Sensors

• Sub-steps:
  1. Remove the upstream oxygen sensor using a socket wrench.
  2. Inspect the sensor's condition; replace if damaged or worn.
  3. Install the new upstream oxygen sensor and torque to the manufacturer specification (typically 30 ft-lbs).
  4. Repeat the process for the downstream oxygen sensor.

3. Inspect and Replace Catalytic Converter

• Sub-steps:
  1. Loosen and remove the exhaust clamps holding the catalytic converter in place.
  2. Remove the bolts securing the catalytic converter to the exhaust pipes.
  3. Inspect the catalytic converter for any signs of blockage or damage.
  4. Install the new catalytic converter, ensuring proper alignment with the exhaust system.
  5. Torque all bolts to manufacturer specifications (usually around 40 ft-lbs).
  6. Reattach exhaust clamps securely.

4. Reconnect Battery and Reset ECM

• Sub-steps:
  1. Reconnect the battery terminals, ensuring they are tight.
  2. Use an OBD-II scanner to clear the P0420 code and reset the engine light.