how to fix my Toyota Highlander XU70 (2020-Present) check engine light P0420?

Solution

1. Preparation

• Gather all necessary tools and parts.
• Disconnect the negative battery terminal to ensure safety while working on the vehicle.
• Ensure the vehicle is on a flat surface and secure it with wheel chocks.

2. Inspect and Replace O2 Sensors

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

• Remove the upstream (pre-catalytic converter) O2 sensor:

  1. Locate the upstream O2 sensor on the exhaust manifold.
  2. Use the O2 sensor socket to unscrew the sensor.
  3. Install the new O2 sensor and tighten it to the manufacturer’s specifications (usually around 30-40 lb-ft).

• Repeat the process for the downstream (post-catalytic converter) O2 sensor if necessary.

3. Inspect and Replace Catalytic Converter (if necessary)

• Tools Required: Socket set, wrench, torque wrench, exhaust gasket, exhaust clamp
• If the catalytic converter is damaged or clogged:
  1. Disconnect the exhaust pipe from the catalytic converter by removing the clamps and bolts.
  2. Remove the old catalytic converter.
  3. Install the new catalytic converter and ensure all connections are tight, torqueing bolts to the manufacturer's specifications.
  4. Replace any gaskets or seals as needed.

4. Reconnect Battery and Clear Codes

• Reconnect the negative battery terminal.
• Use the OBD-II scanner to clear the diagnostic trouble codes.