This procedure covers the replacement of the downstream oxygen sensor on the 2015-2020 Ford F-150 with the 3.5L V6 EcoBoost engine, located after the catalytic converters in the exhaust system.

Warnings

Tools required

Parts

• Downstream O2 sensor × 1 — Use OEM Motorcraft DY-1370 or equivalent

Preparation

1. Park vehicle on level ground and engage parking brake. Chock the front wheels.
2. Ensure engine and exhaust system are completely cool to the touch.
3. Raise the rear of the vehicle and support securely on jack stands at the frame rails.
4. Locate the downstream O2 sensor on the appropriate bank (passenger or driver side), positioned after the catalytic converter in the exhaust pipe.
5. Spray penetrating oil on the O2 sensor threads if visible and allow to soak for 10-15 minutes if sensor is old or corroded.

Procedure

1. 1

   Disconnect O2 sensor electrical connector
   Trace the O2 sensor wire harness back to the electrical connector. Press the release tab and disconnect the connector. The connector may be secured to a bracket with a clip—remove this clip if present.
2. 2

   Remove wire harness from retaining clips
   Follow the sensor wire and release it from any retaining clips or brackets along the exhaust pipe and frame. This provides slack for sensor removal.
3. 3

   Remove old O2 sensor
   Using the O2 sensor socket and ratchet with extension, turn the sensor counterclockwise to remove. The sensor may be tight due to carbon buildup and heat cycling. If resistance is encountered, apply additional penetrating oil and allow to soak, or use a breaker bar for extra leverage. Avoid damaging the exhaust pipe threads.
4. 4

   Clean sensor bung threads
   Use a wire brush to clean the threads in the exhaust pipe where the O2 sensor mounts. Remove all carbon deposits, rust, and old anti-seize compound to ensure proper sealing and torque readings.
5. 5

   Prepare new O2 sensor
   Apply a thin, even coat of anti-seize compound to the threads of the new O2 sensor only. Do not allow any anti-seize to contact the sensor tip or the hexagonal portion that seals against the exhaust pipe. Excessive anti-seize will affect torque readings and may contaminate the sensor.
6. 6

   Install new O2 sensor
   Thread the new O2 sensor into the exhaust pipe bung by hand, ensuring it threads smoothly without cross-threading. Hand-tighten until the sensor is seated against the exhaust pipe.
   Torque spec

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

   Route sensor wire harness
   Route the sensor wire harness along the same path as the original, securing it in all retaining clips and brackets. Ensure the wire has adequate clearance from hot exhaust components, the driveshaft, and any moving suspension parts.
8. 8

   Reconnect electrical connector
   Connect the O2 sensor electrical connector, ensuring it clicks into place securely. Secure the connector to its mounting bracket with the retaining clip if equipped.

Reassembly

1. Lower the vehicle from jack stands and remove wheel chocks.
2. Double-check that the O2 sensor connector is fully seated and the wire harness is properly secured away from heat and moving components.

Verification

• Start the engine and verify there are no exhaust leaks at the O2 sensor location (listen for hissing sounds).
• Using a scan tool, verify the new O2 sensor is providing voltage readings. Downstream sensors typically fluctuate less than upstream sensors and should read 0.4-0.7 volts at steady cruise.
• Clear any diagnostic trouble codes (DTCs) and perform a test drive. Verify the check engine light does not return and the O2 sensor heater circuit is functioning (most scan tools show heater status).
• After a short test drive, re-inspect the sensor installation area for any exhaust leaks that may have developed.

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