what does it mean if my Toyota RAV4 has a P0420 code?

Solution

1. Preparation

• Gather tools and parts needed for repair.
• Disconnect the battery to avoid any electrical issues during repairs.
• Allow the vehicle to cool down if the engine has been running.

2. Inspect and Test Oxygen Sensors

• Remove the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors using an O2 sensor socket.
• Inspect the connectors and wiring for damage or corrosion.
• Test the sensors' resistance with a multimeter; compare readings to specifications in the service manual.
• If faulty, replace the oxygen sensors with new OEM parts.

3. Inspect Catalytic Converter

• Check for physical damage or blockage in the catalytic converter.
• Use a backpressure gauge to measure the exhaust backpressure; it should not exceed manufacturer specifications (usually around 1.5 psi at idle).
• If the converter is clogged or damaged, remove it by unbolting the exhaust flanges and any mounting brackets.
• Replace with a new catalytic converter, ensuring it meets OEM specifications.

4. Reassemble and Reconnect

• Reinstall oxygen sensors in the correct order, tightening to the specified torque (typically around 30 ft-lbs).
• Reattach any exhaust components removed during the inspection.
• Reconnect the battery terminals.