I'd like to make two suggestions. First, my chihuahuas respond VERY poorly to negative reinforcement (scolding, punishment). All they seem to learn from that is to be sneakier about whatever misbehavior they're doing. You have to outthink a chihuahua, which can be tough. The two key points are to reward GOOD behavior instead of punishing bad, and set the chihuahua up to give you excuses to reward.
I've actually never had to deal with the marking issue, but I've dealt with other similar difficult issues like barking, poo eating, etc., and learned a lot from an incredible trainer I took my girls to for obedience training, so let me make a few suggestions. First, boys like to mark on something vertical, so a horizontal pee pad may not be all that appealing. I've heard other male chi owners make some good suggestions for this problem, such as filling up a used liter bottle with sand or rocks and standing it in the middle of the pee pad for a male dog to pee against (I've also heard a log, but the bottle is easily wiped down so it won't hold a smell), or putting a pee pad on the floor next to the wall and also taping a pee pad to the wall as well. When your chi pees in one of the designated spots, or when you let him outdoors, praise and reward like crazy. When he pees somewhere else, there's no point in scolding unless you actually catch him in the act. If you do, say in a firm voice, "No! Not there!" and move him to one of his pee pads, then praise him; if he finishes peeing there, praise and reward like crazy. Dogs usually go back to spots they've marked before. If at all possible, in the beginning put pee pads wherever he marks, unless you can absolutely deny him access to those places. As time goes on, eliminate one spot from the "praise and reward" agenda. He should quickly catch on that although there are pee pads at A, B, C and D, he only gets his reward for A, B and C, and he'll quit using D and you can take down that pad. The fallback suggestion is to find a really good trainer in your area. I strongly advise a trainer who uses positive reinforcement only. My girls went to a clicker trainer. They didn't have any behavior issues; it was just routine obedience training, but Luna was really shy and the training gave her a LOT more confidence. Anne
