how to fix a P0420 code on my Toyota Highlander Fourth Generation (2020-present)

Solution

1. Preparation

• Gather tools and parts required.
• Disconnect the negative battery terminal to prevent electrical short circuits.
• Allow the exhaust system to cool down before starting work.

2. Inspect and Replace Oxygen Sensors

1. Remove the Oxygen Sensors

   • Use an oxygen sensor socket to carefully unscrew the pre-catalytic and post-catalytic oxygen sensors.
   • Disconnect the electrical connectors from both sensors.

2. Inspect the Sensors

   • Check for signs of contamination or damage on the sensors. If they appear faulty, replace them with OEM parts.

3. Install New Oxygen Sensors

   • Apply anti-seize compound on the threads of the new oxygen sensors (if not pre-applied).
   • Install the new sensors by threading them into place and tightening them to manufacturer specifications (typically around 30-40 lb-ft).

3. Inspect and Replace Catalytic Converter (if necessary)

1. Remove the Catalytic Converter

   • Detach exhaust flanges and any hangers securing the catalytic converter using a socket set.
   • Carefully lower the catalytic converter from the vehicle.

2. Inspect for Blockages

   • Check the interior of the catalytic converter for any signs of blockage or damage. If compromised, replace it with an OEM or high-quality aftermarket unit.

3. Install New Catalytic Converter

   • Position the new catalytic converter and secure it using the appropriate exhaust gaskets and hardware.
   • Tighten all bolts to the specified torque value (typically around 25-30 lb-ft).

4. Reconnect Battery and Clear Codes

1. Reconnect the Battery

   • Reattach the negative battery terminal and ensure it is secure.

2. Clear the P0420 Code

   • Use the OBD-II scanner to clear the trouble codes from the ECM.
   • Start the engine and allow it to reach operating temperature.