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

Solution

1. Preparation

• Gather tools and parts.
• Ensure the vehicle is parked on a flat surface and the engine is cool.
• Disconnect the negative battery terminal.

2. Inspect and Replace Oxygen Sensors

1. Locate Oxygen Sensors:
   • Identify the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors under the vehicle.
2. Remove Sensors:
   • Use an oxygen sensor socket to carefully unscrew the sensors from their mounts.
   • Be cautious with any wiring connected to the sensors.
3. Install New Sensors:
   • Apply anti-seize compound on the threads of the new sensors.
   • Screw in the new sensors and tighten them to the manufacturer’s specifications (typically around 30 lb-ft).

3. Inspect and Replace Catalytic Converter (if needed)

1. Remove Exhaust Components:
   • If damage is found or if sensors replacement does not resolve the issue, remove the exhaust components leading to the catalytic converter (bolts and clamps may require penetrating oil).
2. Inspect Catalytic Converter:
   • Check for physical damage, blockage, or contamination.
3. Install New Catalytic Converter:
   • Place the new catalytic converter in position and secure it with bolts and clamps.
   • Tighten to manufacturer specifications (typically around 40-50 lb-ft).

4. Reset the Engine Control Module

1. Reconnect Battery:
   • Reconnect the negative battery terminal after all components have been replaced.
2. Clear Codes:
   • Use the OBD-II scanner to clear the P0420 code from the ECM.