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

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the vehicle is parked on a level surface and the engine is cool.
• Disconnect the battery to prevent any electrical issues during repair.

2. Inspect and Replace Oxygen Sensors

• Locate the upstream and downstream oxygen sensors on the exhaust system.
• Remove the upstream O2 sensor:
  • Use an O2 sensor socket to carefully unscrew the sensor.
  • Disconnect the electrical connector.
• Install the new upstream O2 sensor:
  • Apply anti-seize compound to the threads of the new sensor.
  • Hand-tighten the sensor before securing it with a torque wrench to the manufacturer's specifications (typically around 30 Nm).
• Repeat the process for the downstream O2 sensor if necessary.

3. Inspect and Clean or Replace Catalytic Converter

• Inspect the catalytic converter:
  • Look for physical damage, discoloration, or signs of overheating.
• If cleaning is required:
  • Use a catalytic converter cleaner as per the manufacturer's instructions.
  • Allow the cleaner to work through the system by running the engine for a specified period.
• If replacement is necessary:
  • Unbolt the catalytic converter from the exhaust system using a socket set.
  • Install the new catalytic converter:
    • Align the new converter with the exhaust pipes.
    • Bolt it into place using the appropriate torque specifications (typically around 40 Nm).

4. Reconnect Battery and Clear Codes

• Reconnect the battery terminals.
• Use the OBD-II scanner to clear any trouble codes from the vehicle's memory.

5. Final Inspection

• Start the engine and check for any exhaust leaks around the newly installed components.
• Ensure all electrical connectors are secure and functioning.