2007 tahoe 3ed break light works lowers dont

3ed break light works lowers dont. Cruse control works. Can the break light switch have proper function in cruse control and 3ed break light but not lowers? Checked 2 fusses under hood and one just inside drivers door, good...is there a lower break light relay besides the switch on break peddle? I cleaned up the grounds under thr rear of the truck that aren't bad to begin with but to no avail. Any help with this 07 tahoe would be greatly appreciated.