how to fix P0420 code on Toyota Highlander XU70 (2020-Present)

Solution

1. Preparation

• Gather all necessary tools and parts.
• Disconnect the battery to avoid electrical issues.
• Ensure the vehicle is on a level surface and secure with wheel chocks.

2. Inspect and Replace Oxygen Sensors (if faulty)

• Tools Required: O2 sensor socket, ratchet, torque wrench.
• Remove the upstream (pre-catalytic) oxygen sensor:
  1. Disconnect the electrical connector.
  2. Use the O2 sensor socket to unscrew the sensor from the exhaust manifold.
• Install the new upstream oxygen sensor:
  1. Apply anti-seize compound on the threads of the new sensor.
  2. Torque to manufacturer specifications (typically around 30 lb-ft).
  3. Reconnect the electrical connector.
• Repeat the process for the downstream (post-catalytic) sensor if necessary.

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

• Tools Required: Socket set, torque wrench, exhaust gasket.
• Remove the catalytic converter:
  1. Loosen and remove the bolts connecting the catalytic converter to the exhaust pipes.
  2. Support the converter and remove any mounting brackets.
• Inspect the catalytic converter for physical damage or excessive carbon buildup.
• Install the new catalytic converter:
  1. Position the new converter and secure it with mounting brackets.
  2. Reattach the exhaust pipes and tighten the bolts to the manufacturer’s torque specifications.
  3. Replace any gaskets as necessary to ensure a tight seal.

4. Reconnect Battery and Test

• Reconnect the battery.
• Start the engine and let it idle for a few minutes.
• Perform a test drive to ensure the check engine light does not reappear.