iPhone 5 and Bluetooth

I have an iPhone 5 and bluetooth in my car, I have just noticed that my bluetooth only works when i have my iPod plugged into the car. If I am calling someone on my phone and no iPod my bluetooth does not work and i have to speak to them directly on my phone, this was not the case when my bluetooth was originally set up, any ideas what I can do so my bluetooth always works regardless if my iPod is in or not?

Thanks