There's no sensor for the backup alarm. It's either wired to the reverse lamp switch (or corresponding circuit from the transmission ECU if you're running an Allison) or spliced into the reverse lamp circuit. Either the alarm's not getting power, it's not grounded, or the alarm itself is faulty.
The backup sensor is inside the transmission.
Check Fuses, Replace Bulbs, Replace Shift Position Sensor. End of solution
Since this is not OEM equipment, the answer can vary based on which backup alarm was installed. If the connections at the backup alarm are a ring terminal held in place with a nut and lock washer, you simply disconnect the ground.
Where is back up alarm located
The switches to activate the backup alarm are usually placed within the transmission. If you don't feel like going through this hassle, you can connect the positive wire for the backup alarm to the circuit which activates the backup lights, or you can put a manual switch in the cab to work the backup alarm.
yes u can.
In the alarm panel box or an auxiliary box nearby.
background/histor of lihgt alarm
To help you turn your backup sensor on I would need more information. What does the backup sensor go on? What type of vehicle? What year is it? an what model vehicle is it?
Because you haven't diagnosed it to determine what repair needs to be made. Either it's not getting power, it's not grounded, or the backup alarm itself is toast.
a magnetic theft alarm sensor
how do you replace backup lights on 99 grand am?