Local auto parts stores will show you the fill level mark on the brake fluid reservoir vehicle for free of charge as a gesture of courteous.

the switch is above the brake pedal, on the arm the pedal moves when pressed.

this is a very common thing and I do believe recently GM announced they may be recalling the breaks because of this. My break lights will sometimes stay on, and sometimes will turn off when I push the break down, or I will have to push the break down extremely hard to get the light to turn on.

The brake switch is just above your brake pedal. Every time you press the pedal, it will activate the switch. It can be taken out in less then a minute and replaced. There is no need to play around under the car or above the car or it's engine compartment.

You should be able to simply bleed the brake system - at the wheels (brake caliper) bleeder screws - to remove the contaminated brake fluid. Also, to empty the brake master cylinder - use an old turkey baster to withdraw the brake fluid.
Be sure to refill the brake master cylinder reservoir with fresh, new brake fluid. The residual amount of steering fluid that remains will not hurt anything in the brake system.

Did you use the brakes after you put the wrong fluid in? If not I would just empty the reservoir. It is important to know how much fluid you added and how long ago you did this. If you noticed your error before driving the car and all you did was add a few ounces of power steering fluid, I think you are OK to just empty the reservoir or even just replace the master and bleed the lines. Don't skip bench bleeding the master before you install it.

The abs system stores fault codes. You have to get a code reader that can access the abs system for 08 GM coverage and read fault codes. If you do not learn the codes, you cannot find the cause any other way except guessing by throwing parts at it.

http://www.autopartswarehouse.com/search/

It's about a 2 to 3 hour job. Pick up a repair manual if you plan to do it.

Sounds like a hub bearing. Very common on front, less common on rear axle. Can be a little expensive when done by a repair facility. If you have somewhat of a mechanical aptitude about you it really isn't that hard to do. What you do need to have is an axle nut socket of around 36 mm along with a torque wrench. The axle nut may be torqued on quite a bit so I would suggest using a breaker bar to get it off rather than a ratchet handle. You could possibly trash your ratchet getting it off. A new hub bearing will run from $80 to $110 depending on what kind of warranty you want. A lot of auto parts places will rent you an axle socket but if you're going to keep the car for a while I suggest buying one. I did. I paid $20 for it. The new hub bearing comes with a wire and a socket plug for the ABS so be careful not to damage it during installation.

Try the many on-line auto parts sources, such as; www.autopartswarehouse.com or www.rockauto.com for the replacement parts. For example, they (RockAuto) list the front axle bearing and hub assembly from around $37.00 for your vehicle.
They are not difficult to replace. Check the 'How-To-Guides' feature on the AutoMD website for the specific steps.

Go to a site like Rockauto.com and select those items for the 2004 then check the 'info' link, it gives the year and model applications for that part.

Check each wheel when you have your tires rotated, for a broken wire, this will be your brake senor that is attached to the Hub Assembly......to replace it you will have to purchase the whole Hub Assembly.

I have a 2001 Pontiac GT....It sounds like you might need a Hub Assembly......because the Brake Light senor is broken....this senor is attached to the Hub Assembly ....check to see if this is the same for your car.... it is on the right front wheel of my car.... to save yourself some money have each wheel check when you have your tires rotated to see which wheel... if this is the problem.

The tools needed; lug nut wrench = size: M14, brake caliper wrench (allen and hex) - size: 13mm or 14mm (for the caliper guide pins - both front and rear. Also, buy or borrow (library) a detailed repair manual or guide; such as Haynes, Motor, Chilton - for the repair reference.

You may also refer to the 'How-To-Guides' feature on the AutoMD website for more detail.

Is it the ABS engaging? Does it sound like a buzzing motor turning on while breaking in a turn? If so, you may have a break in the speed sensor wire that may have been aggravated by the brake job. There is a pigtail coming out the back of the hub that goes to a plug mounted on the strut. It then traverses the A arm. Disconnect the plug and hook up an ohmmeter to the hub side. It should be somewhere in the neighborhood of 800-1200 ohms. It shouldn't be an open or dead short, but since you have no abs codes, I'd suspect an intermittent open. If its reading OK, make sure to bend the wire while testing to see if there is any intermittent breaks. If there is, you have two options. Replace the whole hub assembly /VSS......or what I did, chop and solder new wire in. Use high quality, fine stranded copper wire. Also make sure it doesn't rub the CV area (the place where the pigtail exits moves!!!). And the real challenge... Check through entire range of steering for rubbing.

IMO this is a sh1t design to expose cheap aluminum wire to continuous bending, then mount the plug in the freakin' worst spot where snow/ice chunks and roadcrap hits it.

Anyway I had this problem and it didn't throw codes either.

If it's not a abs vibration, maybe the wheel mounting surfaces are not clean. Maybe the lugnuts weren't torqued in steps in the proper order. Maybe the old rotors were reused and have a taper... This was an old post, hopefully you ripped it apart to rectify.

Your front brake rotors are warped from overheating, turning them might fix them. I like to just go ahead and replace them.