squeeks in rear when its cold/bad vibration when driving, what could it be?

What is your question?

I had a 4 wheel alignment done as well as balancing al tires. The squeek in the rear is only when it is cold and any bumps you encounter will cause the back to squeek. Not sure if its related but tire pressure sensor light stays on even when pressure is accurate. I even had it replaced at the dealership. Any suggestions on where to look and what to do would be greatly appreciated.