Are you talking about actual codes, or the OBDII emissions monitors? It sounds like you're talking about the monitors.
If this is indeed the case...
- Check if you have any pending codes (you'll need a scanner, when codes are still pending they don't trigger the check engine light)
- Have you recently disconnected the battery, or replaced any of the emissions components? If so, you'll have to complete several drive cycles for the computer to complete its automatic tests and change the status of the monitors.
- Same thing applies if you recently used a scanner to clear any codes.