how to fix P0420 catalyst efficiency code in Toyota Highlander Fourth Generation (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 avoid electrical shorts.

2. Inspect and Replace Oxygen Sensors

1. Locate the Oxygen Sensors:

   • Identify the upstream (pre-catalytic converter) and downstream (post-catalytic converter) oxygen sensors.

2. Remove the Oxygen Sensors:

   • Use an oxygen sensor socket to unscrew the sensors from their ports.
   • Disconnect the wiring harness from each sensor.

3. Install New Oxygen Sensors:

   • Apply anti-seize compound to the threads of the new sensors.
   • Screw in the new sensors and connect the wiring harness.
   • Torque the sensors to manufacturer specifications (typically around 30 Nm).

3. Inspect and Replace the Catalytic Converter

1. Remove the Exhaust Components:

   • Unbolt the exhaust pipe from the catalytic converter and any hangers holding it in place using a socket set.
   • Ensure to support the exhaust system to prevent stress on connecting components.

2. Inspect the Catalytic Converter:

   • Check for any physical damage, rattling noises, or blockages.

3. Install New Catalytic Converter:

   • Position the new catalytic converter in place and secure it with the bolts.
   • Ensure all gaskets are properly aligned and sealed.
   • Torque to manufacturer specifications.

4. Reconnect Battery and Clear Codes

• Reconnect the battery terminals.
• Use the OBD-II scanner to clear the P0420 code from the ECM.