House breaking a Chihuahua can be difficult if not started on immediately and consistently. If your Chihuahua trusts you, they will be eager to please you. So never spank your Chihuahua for making a mistake when potty training. It is better to praise them when they potty in the correct area.
Puppies can not hold their bladders for very long. Their bladders are very small. Puppies usually have to go to the bathroom as soon as they get up from sleeping! So take them to their spot where you want them to eliminate, immediately after a nap. Their spot can be a potty patch (artificial grass),outdoors, potty pads, or they can even be litter box trained (there is special litter for dogs) As they get older they may not have to go so soon after a nap. When you take them outside get them to follow you around, exercise induces going to the bathroom.
Puppies usually have to go to the bathroom 20 to 30 minutes after eating or drinking, great opportunity to take them outside! Some Chihuahua owners put away all water and food after 6pm, in the hopes they will not need to "go" in the middle of the night. Take your dog outside to toilet before bed time. Set up a regular schedule and your dog will learn much faster, and will know what is expected of him.
Clean up all accidents thoroughly. Even if you can no longer smell it, your dog probably can. If they keep smelling "it" they will believe this is the spot to go "pee" and will repeat the mistake.
So clean it up and then clean it again! There are some great dog urine cleaners on the market. Do not use ammonia for clean ups, smells like urine to your dog. You need to get cleaners specially designed for dog urine. It has enzymes that eliminate the smell to the dog, obviously there are some that do not work as well as others.
Watch your puppy or dog, when they start acting as if they are looking for something, sniffing at the ground or your carpet, floors, or they will start circling around. They are looking for a spot to pee or poop! Take them outside.
Always praise them when they do something that pleases you, especially when they go potty in the proper place! Your Chi puppy and adult Chi lives for your praises. Make a big deal of it, when they potty in the right place. Coo them, get excited, make cheerful, happy sounds, the "attaboy or girl", or "good dog" is music to their ears! Praising your Chihuahua for proper behavior is the sure way to get your Chihuahua to do what you want them to do. Punishing them for bad behavior is not recommended.
Owning an unaltered male is a bigger challenge and somewhat impossible to house train! Is is absolutely natural for the unaltered male to mark his territory. If you have two males, one will "mark", and the other will "mark" over it. Females will also "mark", one female will pee over another female's piddle. If you own a female also that is not altered, every time she comes in heat, your perfectly mannered, house broke male will start marking everything. He is demonstrating to the female, of his virility and that he is "the man",and ready and capable to breed. He is also claiming that this is his territory.
You can show your Chihuahua (puppy, stud, female, altered dog) where he made a "booboo" and sternly tell them no and then take them outside. You can put aluminum foil up against all furniture and objects around the house your Chi is marking. The sound of the urine splashing against the foil frightens them, also it can splash back on him, which he won't like.
Some Chi owners get a water sprayer to control their Chis from distances. A squirt for unwanted behavior, followed by a firm no. This works with some Chis, some don't seem to mind the water. Just be sure you are not squirting for every little thing or just for the fun of it, making it ineffective and very confusing. Remember, it is consistency that teaches your Chi what is expected of him.
The least confusing way and less accidents for you to clean up is simply to crate (confine) them (doggey corral, portable kennel) when you can not supervise them, Chihuahuas are fastidiously clean and most dogs do not like to pee where they sleep. If they do pee inside their crate, they probably couldn't hold it. If they consistently have accidents inside their crate, way after they should of been trained, there may be something wrong physiologically. Seek a veterinarian's advice.
There are all kinds of devices that you can use to aid you in house breaking your Chi and keep them safe. I use exercise pens and portable kennels and potty patch and dog gates. You can also use a child's playpen or portable crib and a child gate for aids. These are all very affordable. The crates with the open wire are used with a blanket covering it.
Please do not constantly keep them penned up. They crave to be with you. They are great snugglers and great bed warmers! Take them out for play time, teaching time, and potty time! Never use their crate or portable kennel as a place of punishment, they will avoid going in there and will not feel safe there. I start out rewarding (treats) my dogs for when I put them in their kennels. Soon they look forward to (crating) any time I ask them. They feel secure there. I always praise them for going into their kennels.
If your Chi is still making "boo boos" after a reasonable amount of time, there is the possibility that your Chi has something physically wrong with him, have your vet check him out. Puppies can not be expected to hold "it" for long periods. Adult dogs can usually wait 8 to 12 hours. All dogs lose their ability to hold it for long periods as they age.
Your Chi wants to please you. Again lots of praise and encouragement. If your dog is not learning, it is not because he is stupid. He simply does not understand what you are asking of him. Keep it simple, so go slowly, be consistent. Plenty of praise and encouragement. If you get an older Chi that has never been properly house broke they will be a little more difficult to train.The learning phase slows with age, and they have old habits to break as well. But if you already own older Chihuahuas that are trained, they can help in teaching the newer dogs the routine! A ramp may also be useful for older Chis.
There are also training aids like diapers for females and belly bands or wraps for males. These are great. You can buy disposable diapers to line the females diaper holder and disposable liners (or just use feminine napkins) to line the males band. They work really well for a female in heat to help with spotting you may get on your furniture. The male belly bands are great also, especially if you have a male that marks. You can put these on when your Chi is out of his kennel or pen and inside the house and you are not supervising well. You can put one of these on and not worry if you can not watch your Chi every moment. These work great for multiple dog homes. Of course they help when potty training also! Buy two or three they are completely washable and if the disposable insert has leaked through, you always have a fresh one to replace it. These are great aids but should not replace housebreaking. If left on for long periods your Chis hair will rub off and they will develop sores from the dampness and rubbing.