How do I find the backup light switch for a 2009 Pontiac g5 automatic transmission

It is possible that you have a bad reverse light switch. It is located on the transmission. Is your PT an automatic or manual transmission?

These lights are all computer controlled ! Several modules involved DIM - dash integrated module , RIM - rear integrated module .They share information on serial data communication network . Class 2 an or GMLAN !
The rear fuse block supplies battery positive voltage through the REVERSE LAMP fuse to the coil and switch terminals of the reverse lamp relay. The DIM sends a power mode message to the RIM indicating that the ignition is in the ON position. When the driver of an automatic transmission equipped vehicle places the gear selector in the REVERSE position, the powertrain control module (PCM) sends a class 2 message to the RIM. The message indicates that the gear selector lever is in the REVERSE position. When the driver places a manual transmission equipped vehicle in reverse the reverse gear position switch mounted on the transmission closes. This provides a ground for the reverse gear position switch signal line, informing the RIM that the transmission is in reverse. For both automatic and manual transmission vehicles the RIM then grounds the control circuit of the reverse lamp relay . This energizes the reverse lamp relay, closing the switch side contacts and providing battery positive voltage to the backup lamp bulbs. The backup lamps are permanently grounded at G402. With both power and ground the backup lamp bulbs illuminate. Once the driver moves the shift lever out of the reverse position a message is send either by class 2 by the PCM or the reverse gear position switch opens causing the RIM to remove the ground from the reverse lamp relay control circuit. This opens the contacts in the relay turning OFF the backup lamps.
This is something best left to the dealer or a ASE certified repair shop . Need a factory or professional grade scan tool to diagnose an repair this . http://www.public.asu.edu/~pheanis/documents/VBI_CAN.pdf

in automatic transmission there is a neutral safety switch, that lets the ECM and BCM know the selected shifter position. check the switch and wiring. in manual trans the reverse switch is mostly located on transmission.

I haven't worked on an escape, but i can tell you that switch is on the transmission.

if fuse and bulbs are fine then it's your reverse switch that's not working. it is located at the transmission, change it. but before changing you should make sure that the wires are not cut or faulty.

My guess would be the neutral safety switch on the transmission.
The switch also acts as a backup light switch when the shifter is in reverse.
I would check for power at the switch for the reverse light circuit.

You will need to either replace or adjust your backup switch, it is located on the transmission next to the shifter. Hope this helps, thank you for using FixYa!

If it is not the bulbs, it may be the fuse.

hello, the back up lights are usually on the same fuse as the tail lights so if they are working it's not a fuse, if the tail lights are not working replace the tail fuse. Otherwise the problem is most the backup light switch, on the manual transmission it's a separate switch located on the transmission on an automatic it is incorporated into the neutral start switch also located on the transmission but on the shaft where the shift selector attaches.

Not sure what transmssion you have but basically it goes from fuse on P/O wire to either the MLP switch on automatic or just a backup lamp switch on manual and leaves the switch on BK/PK wire to the bulbs. Should be easy to trace with a 12v test light.