2007 X5 4.8is, 17000 miles, 4X4 error message, over $5000 repair

[nomadicm]

This is my first post. I really don't know where to get second opinion or help.

My car is 2007 X5 4.8is, bought new and it has only 17000 miles on it.

Recently while I was driving, I had 4X4 and passenger seat belt dysfunction error message. Also the active steering would be disabled as well.

After turning off the vehicle for a while, the vehicle was OK...and had the same problem again.

I got it to one of the dealers.

After a couple of days and over $1500 plus new rear tires for $1300, I got my X5 back. One thing I need to mention is that the service advisor said I needed new rear tires (the front ones were changed a couple of months earlier). If I didn't get new tires, he probably couldn't give me pass on the safety check. I hesitated but wanted to be done with it. So I agreed.

So after $3000, I got my X5 back.

The next day, exactly the same problem occurred!

So the vehicle went back to the shop. And I got an estimate of another $2000-3000 to fix the problem!

My questions:
1. Is it reasonable to be asked to change the tires that had only 17000 miles (normal city driving in warm climate)

2. If the problem was not fixed, does the first time repair cost need to be "refunded"?

3. What would happen if the problem persists after $5000-6000 repair? Would it be another increase of repair cost?

4. The vehicle only has 17000 miles, is it quality problem?

What should I do? Reason with the dealer or contact NA BMW headquarter?

I feel the dealer is trying to rip me off. But I don't really have a sense for. First time to have such high repair bill (warranty expired)

Thank you for helping. I am a full time mom taking care of two young kids. I don't really know cars very well. I was hoping to have a safe and reliable vehicle to drive kids around.