how to fix P0420 error code in Toyota Highlander Fourth Generation (2020-present)

Solution

1. Preparation

• Gather tools and components.
• Ensure the vehicle is parked on a level surface and the engine is cool.
• Disconnect the battery to prevent any electrical shorts.

Tools Required:

• OBD-II scanner
• Socket set
• Torque wrench
• Temperature probe
• Multimeter

2. Inspect and Test Oxygen Sensors

• Sub-step 1: Locate the upstream and downstream oxygen sensors.
• Sub-step 2: Use a multimeter to check the voltage output of the upstream sensor; it should fluctuate between 0.1 to 0.9 volts.
• Sub-step 3: If the upstream sensor is faulty, replace it with a new one.

3. Inspect and Replace Catalytic Converter (if necessary)

• Sub-step 1: Remove any heat shields or components obstructing access to the catalytic converter.
• Sub-step 2: Unbolt the catalytic converter using the socket set.
• Sub-step 3: Inspect the old catalytic converter for physical damage or clogging.
• Sub-step 4: Install a new catalytic converter, ensuring proper alignment and fit.
• Sub-step 5: Torque the bolts to the manufacturer's specifications.

4. Reconnect and Clear Codes

• Sub-step 1: Reconnect the battery.
• Sub-step 2: Use an OBD-II scanner to clear the P0420 code from the ECU.
• Sub-step 3: Start the engine and let it run for a few minutes.