This procedure covers the removal and replacement of the upstream oxygen sensor on the 2021-2024 Ford F-150 with the 3.5L EcoBoost V6 engine.

Warnings

Tools required

Parts

• Upstream O2 sensor (Bank 1 or Bank 2) × 1 — Use OEM specification

Preparation

1. Ensure the engine and exhaust system are completely cool to the touch
2. Raise and support the vehicle on a lift or jack stands if accessing from below
3. Locate the upstream O2 sensor for the affected bank in the exhaust manifold/turbocharger area
4. If the sensor is stuck, apply penetrating oil to the threads and allow 15-20 minutes to soak
5. Disconnect the negative battery cable to prevent accidental fault codes

Procedure

1. 1

   Access the O2 sensor electrical connector
   Locate the upstream O2 sensor wiring harness. The connector is typically secured with a clip or tab. Press the release tab and carefully disconnect the electrical connector from the O2 sensor. Do not pull on the wires themselves.
2. 2

   Remove wire harness clips
   Trace the O2 sensor wire back to any retaining clips or brackets that secure it to the engine or chassis. Release these clips to provide slack for sensor removal. Note the routing for reinstallation.
3. 3

   Remove the upstream O2 sensor
   Using the O2 sensor socket and ratchet with extension, carefully loosen the upstream O2 sensor by turning counterclockwise. The sensor is located in the exhaust manifold near the turbocharger outlet. Once loose, unthread the sensor completely by hand to avoid cross-threading or damage.
   ⚠If the sensor is seized, do not force it. Apply additional penetrating oil and allow more soak time, or carefully apply heat with a torch to the manifold boss area only, avoiding the sensor itself.
4. 4

   Inspect and clean the sensor bung
   Examine the threaded sensor bung in the exhaust manifold for damage or carbon buildup. Use a wire brush to clean the threads thoroughly. Ensure no debris falls into the exhaust system.
5. 5

   Prepare the new O2 sensor
   Remove the new O2 sensor from its protective packaging. Check that the sensor threads are clean. Apply a thin coat of anti-seize compound to the threads only, being extremely careful not to get any on the sensor tip or element. Only a small amount is needed.
6. 6

   Install the new O2 sensor
   Carefully thread the new O2 sensor into the exhaust manifold bung by hand, turning clockwise. Thread it in at least 3-4 full turns by hand to ensure it is not cross-threaded. Once hand-tight, use the O2 sensor socket and torque wrench to tighten to specification.
   Torque spec

   O2 Sensor45 Nm (33 lb-ft)
7. 7

   Reconnect the electrical connector
   Route the O2 sensor wire harness along the original path, ensuring it is not in contact with hot exhaust components or moving parts. Reinstall any wire retaining clips. Connect the electrical connector to the sensor, ensuring it clicks securely into place.
8. 8

   Reconnect the battery
   Reconnect the negative battery cable. This will restore power to the vehicle's electrical systems and allow the PCM to communicate with the new O2 sensor.

Reassembly

1. Ensure all wire routing clips are properly secured and the harness is not touching hot or moving components
2. Double-check that the electrical connector is fully seated and locked
3. Lower the vehicle if raised

Verification

• Start the engine and allow it to reach operating temperature while monitoring for exhaust leaks around the O2 sensor
• Use a scan tool to verify the new O2 sensor is providing a signal and no diagnostic trouble codes are present
• Check that the sensor wiring is not contacting the exhaust system or generating any unusual odors from heat exposure
• Perform a test drive and verify the O2 sensor is responding correctly with live data monitoring if available

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