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

Solution

1. Preparation

• Tools Required:
  • OBD-II scanner
  • Socket set
  • Torque wrench
  • Exhaust pressure gauge
• Safety Warnings:
  • Allow the engine to cool before working on the exhaust system.
  • Wear safety glasses and gloves.

2. Inspect and Replace Oxygen Sensors

1. Disconnect the battery to prevent electrical shorts.
2. Remove the upstream oxygen sensor from the exhaust manifold using a socket wrench.
3. Install the new upstream oxygen sensor and torque it to the manufacturer specifications (usually around 30-40 ft-lbs).
4. Repeat the process for the downstream oxygen sensor if it is suspected to be faulty.
5. Reconnect the battery.

3. Examine and Replace the Catalytic Converter

1. If the catalytic converter is confirmed faulty or inefficient, remove the exhaust pipe connected to the catalytic converter.
   • Use a socket set to remove mounting bolts.
   • Carefully detach any hangers or clamps.
2. Remove the old catalytic converter from the exhaust system.
3. Install the new catalytic converter in the reverse order of removal, ensuring to torque the bolts to the manufacturer's specifications.
4. Reattach any exhaust hangers or clamps securely.

4. Clear Error Codes

1. Use the OBD-II scanner to clear the P0420 code from the ECM.
2. Take the vehicle for a test drive to allow the ECM to recalibrate and check for any reoccurrence of the code.