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

Solution

1. Preparation

• Gather tools: OBD-II scanner, multimeter, infrared thermometer, socket set, safety glasses, gloves.
• Disconnect the negative battery terminal to ensure safety during repairs.

2. Inspect and Replace Oxygen Sensors

1. Locate the Oxygen Sensors:

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

2. Remove the Sensors:

   • Use a socket or wrench to carefully unscrew the oxygen sensors from their locations.
   • Store the sensors safely for inspection.

3. Test the Sensors:

   • Use a multimeter to check the voltage output of each sensor.
   • If the upstream sensor does not fluctuate between 0.1V and 0.9V, it may need replacement.

4. Install New Sensors:

   • Apply anti-seize compound on the threads of the new sensors.
   • Install the new upstream and downstream oxygen sensors, tightening them to manufacturer specifications.

3. Inspect and Replace Catalytic Converter

1. Visual Inspection:

   • Check the catalytic converter for any external damage or signs of blockage.

2. Temperature Test:

   • Use an infrared thermometer to measure the inlet and outlet temperatures of the catalytic converter. A significant difference indicates a failing converter.

3. Remove the Catalytic Converter:

   • Support the exhaust system as needed.
   • Disconnect the catalytic converter from the exhaust manifold and the rest of the exhaust system using a socket set.

4. Install New Catalytic Converter:

   • Position the new catalytic converter and secure it with the appropriate fasteners.
   • Reconnect the exhaust system ensuring all gaskets are replaced as necessary.

4. Reconnect Battery and Clear Codes

• Reconnect the negative battery terminal.
• Use the OBD-II scanner to clear the P0420 code from the system.