how to resolve the P0420 code in my Toyota Highlander Fourth Generation (2020-present)

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure you have a clear workspace and are wearing appropriate safety gear (gloves, goggles).

2. Gather Tools and Parts

• Tools Required:
  • OBD-II scanner
  • Socket set
  • Torque wrench
  • Multimeter
  • Exhaust back pressure gauge
• Parts Required:
  • New catalytic converter (if necessary)
  • Oxygen sensors (if found faulty)
  • Exhaust gaskets

3. Inspect and Replace Oxygen Sensors (if faulty)

1. Locate the oxygen sensors: Identify the upstream and downstream sensors on the exhaust system.
2. Disconnect the battery: To prevent electrical shorts or shocks, disconnect the negative terminal.
3. Remove the faulty oxygen sensor:
   • Use a socket or wrench to unscrew the sensor from the exhaust pipe.
   • Carefully pull the sensor out.
4. Install the new oxygen sensor:
   • Apply anti-seize compound to the threads of the new sensor.
   • Screw in the new sensor by hand and then tighten it using a wrench (do not over-tighten).
5. Reconnect the battery: Reattach the negative terminal and ensure secure connections.

4. Replace Catalytic Converter (if necessary)

1. Disconnect the exhaust system:
   • Use a socket set to remove bolts securing the catalytic converter to the exhaust system.
   • Support the exhaust system as needed to avoid stress.
2. Remove the catalytic converter:
   • Carefully pull the converter from its mounting point.
3. Install the new catalytic converter:
   • Position the new converter and align it with the exhaust system.
   • Install new gaskets and secure with bolts, tightening to the manufacturer's torque specifications.
4. Reassemble exhaust system: Reattach any supports or hangers removed during the process.

5. Clear Codes and Test Drive

1. Clear the P0420 code: Use the OBD-II scanner to reset the check engine light.
2. Test drive the vehicle: Drive under various conditions to confirm that the check engine light does not reappear.