Since you don’t know exactly where the dog urinated on the carpet (I’m assuming there are no tell-tale stains?) then you’re in for a lot of work and expense to get rid of the smell. It’s highly likely that the urine pentrated not just the carpet, but the padding and the subfloor beneath. There are products that could possibly get rid of the smell, such as Nature’s Miracle mentioned above and Urine Gone (www.komotv.com/news/archive/4171231.html), both enzyme eaters. The probelm with these types of cleaners is that they may not work if the areas were already chemically treated in the past to try and remove stains/oder. Also, since you don’t know exactly where the trouble spots are, you’re going to have to treat your ENTIRE carpet, which is going to be expensive and time consuming.
Honestly, the best thing to do would be to try and convince the landlord to replace the carpet and pad altogether. In between the removal of the old carpet and the installation of the new, try to be present so you can look for any tell-tale discolorations on the subflooring that mark heavily saturated areas, and possibly treat those (directly on the wood surface) with an enzyme cleaner. Better yet, if you discover stains on the subfloor, PAINT over them with Kilz Oderless Primer. I know that sounds crazy (painting your subfloor?!), but Kilz seals in oders, even pet oders, and since they’ll be carpeting back over it anyway who’s going to care if there are big white blotches on the subfloor?
I feel for you, as my dog recently passed away and he was sick enough before he did that he urinated several times on the same area of carpet right in front of my home office. Despite attempting to clean it thouroughly, there are some days it smells so bad that I can’t even work in there. I’m having my carpet and padding replaced in a couple of weeks (it needed replacing anyway, the smell is just a catalyst for doing it sooner) and will be treating the subfloor at that time as well.