how to fix P0420 code on my Toyota Highlander Third Generation (2014-2019)

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Allow the engine to cool if it has been running.

2. Inspect and Replace Oxygen Sensors

1. Remove the upstream oxygen sensor:
   • Use an oxygen sensor socket to unscrew the sensor from the exhaust manifold.
   • Disconnect the electrical connector.
2. Install the new upstream oxygen sensor:
   • Apply anti-seize compound to the threads of the new sensor (if applicable).
   • Install the new sensor by hand and tighten to manufacturer specifications (typically around 30 ft-lbs).
3. Repeat the same process for the downstream oxygen sensor.

3. Inspect and Replace Catalytic Converter (if necessary)

1. Remove the catalytic converter:
   • Unbolt the catalytic converter from the exhaust pipe and exhaust manifold using a socket set.
   • Carefully lower the catalytic converter from the vehicle.
2. Install the new catalytic converter:
   • Position the new converter in place and bolt it to the exhaust system.
   • Ensure all connections are tight and secure.
3. Reconnect any heat shields or brackets that were removed.

4. Verify Exhaust System Integrity

• Inspect all joints and connections in the exhaust system for leaks.
• Repair or replace any damaged components as necessary.

5. Reconnect the Battery and Clear Codes

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