Help! Service brake system light on

[vannatta32]

Hey guys. My service brake system light came on but nothing seemed to be wrong and then went off. Now it came on again and it seems like my rear brakes are not working only my front. Haven't had a chance to get it in the shop yet but was hoping maybe somebody has also had this problem can do me a favor and save me some time by pointing me in the right direction of what is wrong. Thanks in advance!

[vannatta32]

Sorry forgot to put info. It is a 2007 gmc Sierra 1500. New style extended cab with the 4.8 if that matters

[gmtech4]

needs to scanned first ,,,sorry ,,that message means there is a code

[txab]

Yep, get it scanned with a reader capable of reading other than engine codes.