You will need a 22 mm wrench.
1. Disconnect the wire from the negative terminal of the battery.
2. Squeeze the latch…
3. …and disconnect the wiring harness connector from the sensor.
4. Loosen the sensor tightening…
Note: Shown with gearbox removed for clarity.
5. …and unscrew it from the gearbox housing hole.
6. To check the switch, connect the tester to its terminals in ohmmeter mode. The resistance should tend to infinity. Press the switch plunger (shown by the arrow) - the resistance should drop to zero. Otherwise, the switch is faulty and must be replaced.
7. Install the reverse light switch in the reverse order of removal.
(This article was borrowed from the website: fordbook)