how to fix P0421 code on Ford F-150 Fourteenth Generation (2021-present)

Learn how to diagnose and fix P0421 exhaust system issue in Ford F-150. Step-by-step guide with diagnostic procedures and repair instructions.

Solution

1. Preparation

• Ensure the vehicle is parked on a level surface and the engine is off.
• Gather tools and parts needed for the repair.

2. Inspect and Replace Oxygen Sensors

1. Identify the Location: Locate the upstream oxygen sensor (pre-catalytic converter) on bank 1.
2. Disconnect Battery: Disconnect the negative battery terminal to ensure safety.
3. Remove the Sensor: Use an oxygen sensor socket to remove the upstream oxygen sensor.
4. Install New Sensor: Apply anti-seize compound to the threads of the new oxygen sensor and install it, tightening it to manufacturer specifications (usually around 30 ft-lbs).
5. Reconnect Battery: Reconnect the negative battery terminal.

3. Inspect and Replace Catalytic Converter (if necessary)

1. Assess Condition: If the oxygen sensor replacement does not resolve the P0421 code, inspect the catalytic converter for internal blockage or damage.
2. Remove Exhaust Components: If replacement is needed, safely lift the vehicle and remove any exhaust components obstructing access to the catalytic converter (use a socket set).
3. Install New Catalytic Converter: Position the new catalytic converter and secure it using new gaskets and bolts as per manufacturer specifications.
4. Reattach Exhaust Components: Reassemble any removed exhaust components, ensuring all connections are tight to prevent leaks.

4. Clear Codes and Test

1. Reset the ECM: Use the OBD-II scanner to clear the P0421 code.
2. Test Drive: Conduct a test drive to ensure the vehicle operates correctly and monitor for any reoccurrence of the P0421 code.