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

Solution

1. Preparation

• Ensure the vehicle is parked on a level surface and the engine is cool.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Gather necessary tools and parts.

2. Inspect Oxygen Sensors

• Locate the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
• Using an OBD-II scanner, check the voltage readings during idle and acceleration.
• If readings are out of range (usually 0.1-0.9 volts for pre-catalytic), replace the faulty oxygen sensor(s).

3. Check Exhaust System

• Visually inspect the exhaust manifold, pipes, and the catalytic converter for any signs of leaks or damage.
• Tighten any loose connections and replace any damaged sections of the exhaust system.

4. Replace Catalytic Converter (if necessary)

• If the catalytic converter is found to be damaged or contaminated:
  • Remove the necessary exhaust components, starting with the bolts or clamps securing the converter.
  • Carefully detach the catalytic converter from the exhaust system.
  • Install the new catalytic converter, ensuring proper alignment.
  • Torque the bolts to the manufacturer’s specifications (typically 30-50 ft-lbs).

5. Reset the Engine Control Module (ECM)

• Reconnect the negative battery terminal.
• Use the OBD-II scanner to clear the P0420 code from the ECM.
• Start the engine and allow it to reach operating temperature.