While going in reverse mode Fuse number 27 blows on Ford Ranger?

In this case my customer noticed problem while going in reverse.
But if the car is directly shifted to drive mode,the fuse does not blows.

As per 1999 ford ranger details
Fuse 27 covers the electric shift, backup lamps, day time running lamps,TCU, and vacum hub lock.
On that basis the troubleshooting is as follows :----

First off,see if the brake lights are coming on,when brake pedal is depressed.
If not,then brake light bulb is faulty.
In many of such cases the problem was brake light bulb.The bulb blows out and this causes the issue.

But if brake light bulbs are working very fine then read further

If the fuse only blows when you put it into rev, then there is a short some were after the switch on the transmission to the back up lamps , the wire that has the short in it is violet/orange from the nutrial saftey switch on the transmission to the back up lamps, so you have to start at the trans and follow the harness to the rear of the truck to the back up lamps looking for shorts in this wire .If you have any add on stuff tied into the system , then disconect it and see if the short is gone , like a back up beeper, or add on trailer wiring , look under the rear bumper and check the wiring there for any add on stuff .Also remove the back up lamp bulbs and check the sockets for damage.

This details will help.
Thanks.

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