how to diagnose P0420 error code in my Toyota Camry Eighth Generation (2018-present)

Solution

1. Preparation

• Tools Required: OBD-II scanner, multimeter, socket set, torque wrench, exhaust leak tester.
• Safety Warnings: Allow the engine to cool before working on the exhaust system. Disconnect the battery before servicing electrical components.

2. Replace Faulty Oxygen Sensors

• Step 1: Disconnect the battery.
• Step 2: Locate the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
• Step 3: Use a socket set to remove the faulty oxygen sensors.
• Step 4: Install the new sensors and torque them to the manufacturer’s specifications (usually around 30-40 ft-lbs).
• Step 5: Reconnect the battery.

3. Replace the Catalytic Converter (if necessary)

• Step 1: Raise the vehicle securely on jack stands.
• Step 2: Remove the exhaust system components leading to the catalytic converter (use penetrating oil if bolts are seized).
• Step 3: Unbolt the old catalytic converter from the exhaust manifold and the exhaust pipe.
• Step 4: Install the new catalytic converter and torque the bolts to the manufacturer’s specifications (typically 25-35 ft-lbs).
• Step 5: Reattach the exhaust components and ensure all connections are secure.