how to fix P0421 code on Ford F-150 13th Generation (2015-2020)

Learn how to diagnose and fix P0421 exhaust system issue in Ford F-150 (2015-2020). Step-by-step guide with diagnostic procedures and repair instructions.

Solution

1. Preparation

• Gather all necessary tools and parts.
• Disconnect the negative terminal of the battery to prevent electrical shock.

Tools Required:

• OBD-II scanner
• Socket set
• Torque wrench
• Multimeter
• Exhaust pipe cutter (if needed)

2. Inspect and Replace Oxygen Sensors

• Sub-step 1: Remove the upstream (pre-catalytic) oxygen sensor by disconnecting its electrical connector and using a socket to unscrew it.
• Sub-step 2: Install the new oxygen sensor and torque it to the manufacturer’s specifications (typically around 30 lb-ft).
• Sub-step 3: Repeat for the downstream (post-catalytic) oxygen sensor if needed.

3. Inspect and Replace the Catalytic Converter

• Sub-step 1: Remove the exhaust pipes connected to the catalytic converter using a socket set.
• Sub-step 2: If the catalytic converter is clogged or damaged, remove it completely. Use an exhaust pipe cutter if necessary.
• Sub-step 3: Install the new catalytic converter, ensuring proper alignment with the exhaust system.
• Sub-step 4: Torque all bolts to the manufacturer’s specifications.

4. Reconnect Battery and Test

• Sub-step 1: Reconnect the negative battery terminal.
• Sub-step 2: Start the engine and let it idle for a few minutes.
• Sub-step 3: Use the OBD-II scanner to check if the P0421 code has been cleared and ensure no new codes have appeared.