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

Solution

1. Preparation

• Gather tools and parts required.
• Disconnect the negative battery terminal to prevent electrical issues.
• Allow the vehicle to cool down completely before starting work.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, ratchet, torque wrench.
• Steps:
  1. Locate the upstream (pre-catalytic converter) and downstream (post-catalytic converter) oxygen sensors.
  2. Disconnect the wiring harness from each sensor.
  3. Use the O2 sensor socket to remove the sensors from their respective locations.
  4. Install new oxygen sensors by threading them in by hand to prevent cross-threading.
  5. Torque to manufacturer specifications (usually around 30-40 ft-lbs).
  6. Reconnect the wiring harness to the new sensors.

3. Inspect and Replace Catalytic Converter

• Tools Required: Socket set, torch (if necessary for stuck bolts), exhaust gasket, torque wrench.
• Steps:
  1. Locate the catalytic converter in the exhaust system.
  2. Remove any bolts or clamps securing the catalytic converter to the exhaust pipes.
  3. If necessary, heat the bolts with a torch to break any rust or corrosion.
  4. Remove the old catalytic converter and inspect the exhaust pipes for damage.
  5. Install the new catalytic converter and ensure proper fit with exhaust gaskets.
  6. Torque the bolts to manufacturer specifications (typically around 25-30 ft-lbs).

4. Reset the Engine Control Module (ECM)

• Reconnect the negative battery terminal.
• Use the OBD-II scanner to clear the P0420 code from the ECM.
• Start the vehicle and allow it to reach operating temperature.