dettol multi-surface cleaner diluted to anti-bacterial strength gets most of the smell out (as long as you don't put your nose right on the carpet), but I don't know if it will affect your scotch guard. If the dog pee is dry, you could try rubbing in some bicarbonate of soda powder and vacuum it out. Or you could try white vinegar - that's quite good at getting rid of 'organic' odours. Steam cleaning works better - could you rent one? Lots of dry cleaners and hardware shops rent out carpet cleaners.
My dog treats the spare bedroom as his own private loo if I don't shut the door, which is why I've tried so many different things to get rid of the aftermath