2001 GMC Jimmy backup lights

Hello, I'd check the fuses and fuse circuit. Also chek the back-up lamp switch, should be on the trans housing. The fuses should be in the underhood fuse block. My info shows the fuse goes hot when you turn the key on.

i had checked fuse and is good it seems there is no power at switch on transmisson definitly no power at rear back up lights bulb is good

Check the B/U lamp fuse 25 amp in the underhood fuse box. That circuit should be hot with the key on, even if the fuse is ok, if there is no voltage feed, it won't matter.