how to fix P0420 code on Toyota Corolla E140 (2006-2013)

Solution

1. Preparation

• Gather necessary tools and parts before starting the repair.
• Tools Required: OBD-II scanner, socket set, torque wrench, multimeter, oxygen sensor socket, exhaust system jack stands, backpressure gauge (if needed).
• Park the vehicle on a flat surface and ensure the engine is cool.

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 Battery: Remove the negative terminal from the battery to prevent electrical shorts.
3. Remove the Sensors: Using an oxygen sensor socket, carefully unscrew the sensors from their respective locations.
4. Install New Sensors: Apply anti-seize compound to the threads of the new sensors, then install them by hand to avoid cross-threading. Tighten to manufacturer specifications (typically around 30 lb-ft).
5. Reconnect the Battery: Reattach the negative battery terminal.

3. Replace the Catalytic Converter (if necessary)

1. Support the Exhaust System: Use jack stands to support the exhaust system safely.
2. Remove Exhaust Components: Disconnect the exhaust pipes and heat shields as necessary, taking care to unbolt any flanges or clamps.
3. Remove the Catalytic Converter: Unscrew the bolts securing the catalytic converter to the exhaust manifold and the exhaust pipe. Carefully remove the converter.
4. Install New Catalytic Converter: Position the new catalytic converter and secure it with bolts, ensuring proper alignment. Torque bolts to manufacturer specifications (generally around 30-40 lb-ft).
5. Reassemble Exhaust Components: Reattach the exhaust pipes and heat shields, ensuring all connections are tight.