What's the Honda Pilot code a123?

So, the Honda Pilot "code" You speak of isn't really a code at all -- at least not how we think of it in a traditional car sense. You might think You're looking for something like an OBD-II fault code, when in reality, the system You've discovered is Honda's way of sending You service reminders. At certain intervals, alphanumeric characters will illuminate on Your dash. In short, A123 indicates that You need to replace engine oil (but not the oil filter), rotate Your tires, check Your tire pressure and condition, replace Your air cleaner, check Your drive belt, replace Your cabin air filter, replace Your transmission fluid, and finally replace Your transfer fluid if You have it. You might see additional characters like 4, 5, and 6 pop up sooner than later, so be ready for a few more maintenance items when the time comes.