how to fix P0421 code on Ford F-150 14th Generation (2021-2024)

• •Check engine light illuminated
• •Reduced engine performance
• •Increased emissions
• •Poor fuel economy
• •Unusual exhaust odors

1. 1Scan the vehicle using an OBD-II scanner to confirm the P0421 code and check for any additional trouble codes.
2. 2Inspect the exhaust system visually for any signs of damage or leaks, particularly around the catalytic converter.
3. 3Check the oxygen sensors' operation; use a multimeter to verify their voltage output.
4. 4Measure the temperature before and after the catalytic converter using an infrared thermometer to assess its efficiency.
5. 5Inspect for any vacuum leaks in the intake system that could affect the air-fuel mixture.
6. 6Review service history for any previous repairs related to the exhaust or emissions system.

After completing the repair, verify that the issue has been resolved:

• ✓Test the affected component to ensure it functions correctly
• ✓Check for any error codes or warning lights
• ✓Monitor the vehicle for a few days to ensure the issue does not recur

To prevent this issue from occurring again:

• •Follow the manufacturer's recommended maintenance schedule
• •Address warning signs early before they develop into major issues
• •Use quality parts and fluids recommended for your vehicle
• •Keep detailed records of all repairs and maintenance

• •OBD-II scanner
• •Multimeter
• •O2 sensor socket
• •Ratchet
• •Torque wrench
• •Cutting torch
• •Socket set
• •Infrared thermometer

• •Oxygen sensors (if needed)
• •Catalytic converter (if needed)