When trying to set in a CAR ID, the manual says that it can hold up to 9 digits or letters, but initially I was only able to set in 3 digits. The manual is NOT clear on how to do this. I finally realized that the letters CAR ID are a part of those 9 letters or digits. This is NOT stated in the manual. The way to get all the letters or digits is to use the little back arrow at the bottom of the menu and delete the CAR ID letters. THEN you may enter the full 9 digits or letters.