how to fix P0421 code in Toyota Tacoma N300 (2016-Present)

Learn how to diagnose and fix P0421 warm up catalyst efficiency issue in Toyota Tacoma N300. Step-by-step guide with diagnostic procedures and repair instructions.

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the vehicle is parked on a flat surface and the engine is cool.
• Disconnect the battery to prevent electrical short circuits.

2. Inspect and Replace Oxygen Sensors

1. Locate the upstream oxygen sensor (pre-catalytic converter).
2. Use an oxygen sensor socket to remove the old sensor.
3. Install the new oxygen sensor, ensuring it is tightened to the manufacturer's specifications (typically around 30 Nm).
4. Repeat the process for the downstream oxygen sensor if necessary.

3. Inspect and Replace Catalytic Converter

1. Raise the vehicle using a jack and secure it with jack stands.
2. Remove the exhaust heat shield, if applicable, to access the catalytic converter.
3. Unbolt the catalytic converter from the exhaust manifold and the exhaust pipe using a socket set.
4. Inspect the gaskets and replace if damaged.
5. Install the new catalytic converter, ensuring proper alignment and torque specification (typically around 40 Nm).
6. Reinstall the heat shield if removed.

4. Check Exhaust System for Leaks

1. Perform a visual inspection of the entire exhaust system.
2. Use soapy water to identify any leaks; bubbles will form if there is a leak.
3. Repair or replace any damaged sections of the exhaust system.

5. Reconnect Battery and Clear Codes

1. Reconnect the battery terminals.
2. Use the OBD-II scanner to clear the trouble codes from the vehicle's computer.