how to diagnose P0420 code on my Toyota RAV4 Fifth Generation (2019-present)

Solution

1. Preparation

• Gather tools: OBD-II scanner, multimeter, socket set, torque wrench, and safety goggles.
• Disconnect the vehicle's battery to prevent electrical shorts.
• Allow the engine to cool before working on the exhaust system.

2. Inspect and Replace Oxygen Sensors

• Sub-step 1: Remove the upstream oxygen sensor (pre-catalytic converter) using a socket wrench.
• Sub-step 2: Test the sensor with a multimeter to ensure it is within specifications (typically 0.1 to 0.9 volts when the engine is running).
• Sub-step 3: If the sensor is faulty, install a new one and reconnect the wiring harness.

3. Examine and Replace the Catalytic Converter

• Sub-step 1: Remove any heat shields or brackets securing the catalytic converter.
• Sub-step 2: Unbolt the catalytic converter from the exhaust system using a socket set (note the torque values for reinstallation).
• Sub-step 3: Inspect the catalytic converter for signs of clogging or damage; if damaged, replace it with a new component.
• Sub-step 4: Install the new catalytic converter and ensure all bolts are torqued to the manufacturer's specifications.

4. Clear Codes and Test Drive

• Sub-step 1: Reconnect the battery.
• Sub-step 2: Use the OBD-II scanner to clear the P0420 code from the system.
• Sub-step 3: Start the engine and take the vehicle for a test drive to ensure the check engine light does not reappear.