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

Solution

1. Preparation

• Tools Required: OBD-II scanner, multimeter, oxygen sensor socket, temperature probe, basic socket set, jack and jack stands.
• Disconnect the battery to prevent electrical shorts and ensure safety while working on the vehicle.

2. Inspect and Replace Oxygen Sensors

• Sub-steps:
  1. Locate the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors on the exhaust system.
  2. Use the oxygen sensor socket to remove the upstream sensor.
  3. Inspect for corrosion or damage and replace if necessary.
  4. Repeat for the downstream oxygen sensor.
  5. Reconnect the battery and clear the P0420 code using the OBD-II scanner.

3. Inspect and Replace Catalytic Converter (if necessary)

• Sub-steps:
  1. Raise the vehicle using a jack and secure with jack stands.
  2. Inspect the catalytic converter for any signs of damage, rattling, or blockage.
  3. If replacement is needed, unbolt the catalytic converter from the exhaust system using a socket set.
  4. Install the new catalytic converter, ensuring to torque the bolts to the manufacturer’s specifications (typically around 30-45 ft-lbs).
  5. Lower the vehicle and reconnect the battery.