This Checkpoint will only become accessible once you visited Iron Butte (ripper territory) as part of the story. There are several Rippers occupying this checkpoint, including a heavy machine-gunner. There’s a hole in the fence to the left where you can enter so you can take out the rippers silently. It’s relatively safe in this location to go loud and take them out using your Guns.
The generator is located along the road, beside a cargo truck. From the generator’s location, turn around to see a bonfire. The gas can is right beside the blue portalet.
Disable the speakers on top of the two MMUs, one speaker on a light pole near the police car, one speaker on the guard booth in the road-side entrance of the Checkpoint, and another speaker on the light pole between the tents.
Once done, juice up the generator and power it up to restore the power. The Injector is located in the MMU to the north. Loot the NERO Injector from the hard case beside the door to clear this Checkpoint.