The power steering isn't working. The reservoir was empty and I added power steering fluid and it still very hard to steer

If you can't find a power steering fluid reservoir under the hood in the engine compartment your G6 could have Electronic Power Steering . If you look up under the dash below the steering column you will see a electric motor mounted to the steering column !
The power steering system reduces the amount of effort needed to steer the vehicle. The system uses the powertrain control module (PCM), body control module (BCM), power steering control module (PSCM), discrete battery voltage supply circuit, steering shaft torque sensor, steering wheel position sensor, power steering motor, driver information center (DIC), and the serial data circuit to perform the system functions. The PSCM and the power steering motor are serviced as an assembly and are serviced separately from the steering column assembly. The steering shaft torque sensor and the steering wheel position sensor are not serviced separately from each other or from the steering column assembly. The steering column assembly does not include the power steering motor and module assembly.

Is it making a groaning noise? The power steering fluid reservoir might be empty. Very low tire pressure also causes hard steering.

no noise when turning and stiff steering is usually narrowed down to 2 things. a bad power steering pump or bad rack and pinion assembly. the rack and pinion is most of the time leaking fluid when it is bad, but you stated the fluid is good. I suggest to remove the power steering reservoir cap , start the engine and look inside the reservoir. the fluid should be swirling if the pump is working especially when turning the steering wheel. if the fluid isn' t moving then the pump is most likely bad.

It sounds as if you have a volume of air in your power steering system. This is causing the bubbling and also some of the noise you might be generating when you turn the wheels hard right or hard left. This air might have been introduced if your old belt was slipping so much that the pump was essentially not operating and fluid wasn't regularly circulating throughout the system. Another, more expensive possibility is that your old belt was slipping because the power steering pump itself was starting to fail, and the new, grippier belt is turning the damaged pump and showing you its lack of functionality.
The first and easiest thing to do would be to bleed the system. Open the hood and take the cover of the power steering fluid reservoir. With the engine off but the steering wheel unlocked, slowly turn the steering wheel all the way to one side and then to the other. Repeat this several times while watching the power steering reservoir. Is the fluid bubbling? If so, good, you're purging air out of your system. In general, this is easier with the front wheels off the ground, but that is not absolutely necessary (if you have strong arms).
Once you have purged the system, put the cap back on the power steering reservoir, topping it off if the fluid level has dropped to the fill mark. Now, restart your car and observe the power steering pump. Does it seem to be operating quietly and smoothly? If you touch the pump 1-2 minutes after the engine has been running, is it hot to the touch? It will probably be warm, but _hot_ is an indication that something is overheating inside the pump. Is the power steering fluid very dark colored or does it smell burned? This is also a sign that the fluid should be changed ASAP and that some internal damage may have occurred. Burned fluid isn't necessarily an indication that your power steering pump is bad. However, if after changing your PS fluid the new fluid quickly becomes dark and starts smelling burned, then it's probably time to start saving money for a new or rebuilt power steering pump.

is there oil everywhere? Is the power steering resivour low, or empty? Is the drive belt for the pump still there? Check for these things first, and come back on here for more help...

Locating the Power Steering reservoir and adding PS fluid. 1999 Pontiac GP

The reservoir is clearly visible in the engine bay on the 3.1 litre engine cars.

For the 3.8 Ltr engine cars, use a flashlight to look down past the alternator for a black cap with a steering wheel printed on it to indicate the power steering fluid reservoir. ( passenger side of the vehicle).

Remove the cap of the power steering reservoir, clean the dipstick, re-insert and remove again to check the fluid level. If the level is at or below the low level mark, add fluid slowly, taking care not to fill above the MAXIMUM mark. It's best to add small amounts and re-check the level as you go to ensure you do not overfill the reservoir above the MAX level.

ONLY use the power steering fluid recommended for that vehicle by GM.

When u fill; up the reservoir means u have a fluid leak!
Did u check where could be the leakage coming from?

You really can't flush out the steering system fluid other then siphoning the fluid out of the steering pump reservoir. This is the easy way.
The hard way:
Remove the filler cap from the top of your power steering system then disconnect the reservoir's hose. It should be located on the bottom of the reservoir. The hose can be tough to remove, so make sure you have plenty of patience.

Replace the reservoir's hose with another hose. It should lead to an empty container. You'll use this container to store the old power steering fluid as it leaves the reservoir. Lift the front end of your car off the ground by using a car jack.

Add new power steering fluid to the reservoir. As you add the new lubricant, it will force the old lubricant into the tube you've connected to the bottom of the reservoir.

Climb into the drivers seat and rack your steering wheel back and forth. The wheel should be locked in place, allowing only a slight range of mobility. This will help the extra lubricant within the power steering system to drain.
Watch the empty container. It should fill with old lubricant. Once the old lubricant has been flushed and you see clean fluid replacing it, you've finished the hard part.

Disconnect your hose and move the container. Replace the original reservoir hose. Pour new, clean power steering fluid into the reservoir. Rack your steering wheel a few more times to squeeze out air that might be trapped in the lines. Replace the filer cap and close your done.
Thank you for suing fixya and good luck

power steering need bleeding if your reservoir was dry when you added fluid if.fluid was okay not too low.your power steering pump could be faulty.the cold weather will effect it.

Make sure the fluid level is OK, if reservoir MT ad, with out the cap till air comes out and fluid gets in to system, turn the steering right to left wile You add fluid with cap off, till fluid is not longer going down and reservoir inside gets quiet, when fluid level is OK, put cap back and try it, if system did not recovered normality and loud noise comes from the pump, pump needs replacing, if steering is steel hard, no noise comes from pump, look a steering box or steering arms, if truck has Rakenpinon, look for broken boots, pit man arm