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

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the battery to ensure safety during repairs.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, ratchet, torque wrench

• Remove the upstream O2 sensor:

  1. Locate the upstream oxygen sensor (before the catalytic converter).
  2. Use the O2 sensor socket to unscrew the sensor.
  3. Install the new O2 sensor and tighten it to the manufacturer's specification (usually around 30 ft-lbs).

• Remove the downstream O2 sensor:

  1. Locate the downstream oxygen sensor (after the catalytic converter).
  2. Use the O2 sensor socket to unscrew the sensor.
  3. Install the new O2 sensor and tighten to specification.

3. Inspect and Replace the Catalytic Converter (if necessary)

• Tools Required: Socket set, jack and jack stands, exhaust clamp tool

• Raise the vehicle and secure it with jack stands.

• Remove the exhaust components:

  1. Unbolt the exhaust pipe from the catalytic converter using the socket set.
  2. Remove any hangers or clamps securing the catalytic converter.

• Install the new catalytic converter:

  1. Position the new catalytic converter in place.
  2. Reattach the exhaust pipe and ensure all connections are tight.
  3. Reinstall any hangers or clamps that were removed.

4. Reconnect and Test

• Reconnect the battery.
• Start the vehicle and allow it to reach operating temperature.
• Clear the P0420 code using the OBD-II scanner and take the vehicle for a test drive to ensure the check engine light does not reappear.