I am replacing the brake pads on my Kia 2007 Sedona; front and back is neeeded or just front? Took it to Kia dealer and mechanic showed me pads where very thin and needed replacement; all for $400! Heck no. I'll do it myself ??? what brand do you recommend? ceramic is good?

Then the new parts did not cure the fault. Do another fault code test and see what shows up, if the same fault codes pop up then you may have a wiring issue or the control module is defective (very unlikely)

Usually if the booster fails, the pedal is very hard to push enough to make the vehicle stop.
If the pedal sinks or is soft, the master cylinder is allowing fluid to bypass the pistons inside.

https://www.google.com/search?q=2003+Kia+Sedona+Rear+Brakes+diagram&oq=2003+Kia+Sedona+Rear+Brakes+diagram&sugexp=chrome,mod=0&sourceid=chrome&ie=UTF-8

I had the same problem with my 2007 kia optima. Replaced the pads at about 30k, The pads tend to get stuck and not fully release from the rotor. I took mine to the dealership at around 45k and they replaced the calipers and pads under warranty. According to the dealership the rear brakes are suppose to be serviced every 15k to prevent this from happening

How to reset the airbag light on in a 2002 KIA Sedona

take your old brake pads with you to compare. may need to go to a kia dealer.

I have a similar problem with my kia sedona 2003. The kia dealer told me to have the disc pads replaced. I brought it to a brake pads bonding shop cause its cheaper to replace there. But the thinnest pad are still half thick. The real problem was on the back plate, it's touching on the brake disc making the sound and scratching it. Just push the back plate away from the disc to solve the problem. If I have known this I could have used those disc pads for a few more months.

do one side at a time so you can have somthing to go on.

We're on our second Sedona and have had this problem on both. In our case it was the front brake rotors. The dealer told me that they're not made thick enough to handle heat loads. They are super-sensitive to heating and warp easily.

With my Sedonas the pads were not retracting completely, sometimes dragging on the rotors (not enough to notice this while driving) causing them to heat even when the brakes were not being applied and causing this front end shaking in the steering wheel when braking. When it got worse, the brake pedal would vibrate too. When we would take it up the mountains the long braking periods on the downslopes would make it much worse as the rotors heated up. The dealership had them machined but the issue persisted and ended up replacing the front rotors.

Replacing rotors is not a difficult task if you're mechanically-inclined and have the right tools. I've done it on many vehicles (though not my Sedonas as they were warranty jobs) and it's usually less expensive to replace them with new ones from your parts store than to have a brake shop work on them.

Hope this helps.

Does the key turn?  If so, the problem may be that the interlock mechanism is jammed and not letting the pawl drop into the steering column to lock it.  You may need a dealer or other professional to fix this.  The air bag is involved.