why does my Toyota Highlander XU70 (2020-Present) have a check engine light on with code P0420?

Solution

1. Preparation

• Gather tools and parts: OBD-II scanner, multimeter, infrared thermometer, socket set, and safety equipment (gloves, goggles).
• Disconnect the vehicle's battery to prevent any electrical shorts during the repair.

2. Inspect and Replace Oxygen Sensors

• Sub-steps:
  • Locate the upstream (pre-catalytic converter) and downstream (post-catalytic converter) oxygen sensors.
  • Disconnect the electrical connectors from both sensors.
  • Use a socket wrench to remove the sensors from the exhaust manifold and exhaust system.
  • Install new oxygen sensors and torque them to the manufacturer's specifications (usually around 30 lb-ft).
  • Reconnect the electrical connectors.

3. Check and Replace Catalytic Converter (if necessary)

• Sub-steps:
  • Inspect the catalytic converter for physical damage or blockage.
  • If replacement is necessary, unbolt the catalytic converter from the exhaust system using a socket set.
  • Clean any exhaust manifold or pipe surfaces to ensure a proper seal for the new converter.
  • Install the new catalytic converter, ensuring proper alignment and torque to the specified values (typically 30-40 lb-ft).
  • Reconnect any exhaust hangers or brackets.

4. Reconnect Battery and Reset Codes

• Reconnect the battery terminals and ensure they are secure.
• Use the OBD-II scanner to clear the P0420 code and check for any new codes after starting the engine.