The reason you are having an issue finding it is because Ford only used one rear sensor in the rear differential on these trucks.
I attached the process below from the manual. Please run through this material and let us know if you have other questions. Thanks
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Jul 2, 2021 at 7:29 AM
Repair Safety Notice: This information is for general instructional purposes only. Vehicle repair can be dangerous. Verify all information, follow manufacturer service procedures, use proper tools and safety equipment, and consult a qualified repair shop when needed.