why is my Toyota RAV4 XA40 (2013-2018) check engine light on with code P0420

Solution

1. Preparation

• Gather tools and parts needed.
• Ensure the vehicle is parked on a level surface.
• Disconnect the negative battery terminal to prevent electrical shorts.

Tools Required:

• OBD-II scanner
• Socket set
• Torque wrench
• Multimeter
• Exhaust gas temperature (EGT) probe

2. Inspect and Replace Oxygen Sensors (if necessary)

1. Locate the Oxygen Sensors: Identify the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
2. Disconnect the Sensors: Carefully unplug the electrical connectors from each oxygen sensor.
3. Remove the Sensors: Use the appropriate socket to unscrew the sensors from the exhaust pipes.
4. Test the Sensors: Use a multimeter to check the voltage output of the sensors. Replace any sensor that is outside of the manufacturer's specifications.
5. Install New Sensors: If replacing, apply anti-seize compound to the threads of the new sensors and install them into the exhaust, tightening to the manufacturer’s torque specifications.

3. Inspect and Replace Catalytic Converter (if necessary)

1. Visual Inspection: Check the catalytic converter for any dents, cracks, or signs of overheating (discoloration).
2. Exhaust Flow Test: If the catalytic converter seems blocked, conduct an exhaust flow test by measuring back pressure to confirm restriction.
3. Remove the Catalytic Converter: Unbolt the catalytic converter from the exhaust system using a socket set, taking care to support it while removing.
4. Install New Catalytic Converter: Position the new catalytic converter in place and secure it with the bolts. Ensure all gaskets are replaced as needed.
5. Torque Specifications: Tighten the bolts to the manufacturer’s specifications.

4. Clear Codes and Test

1. Reconnect Battery: Reconnect the negative battery terminal.
2. Clear Trouble Codes: Use the OBD-II scanner to clear the P0420 code from the vehicle's computer.
3. Test Drive: Take the vehicle for a test drive to monitor the check engine light and ensure proper operation.