My husband and I are native Californians for over forty years and have many, many years of experience with the police and sheriffs in situations from being pulled over for a dead headlight on the car to supposed criminal activity. The bottom line answer is absolutely. Whatever the circumstances are, whether or not you have or have not done anything illegal, you must upon a peace officer's request, provide a state's drivers license or ID card. If you do not, and we have had many times when we didn't have ID for various reasons, they will keep hammering at you to provide your name, address, date of birth so they can verify this by searching extensive computer databases (and their patrol cars have extremely high tech equipment besides loaded guns, assault rifles, mace, taser guns that they're trained and ready to use) until they feel satisfied. It is extremely important that you realize the police here take this totally seriously and do not try to skirt around the issue with what you feel may or may not be probable cause. They instantly will be suspicious that you are hiding something by not having any ID on your person or refusing and this can lead to more problems than you might think. There have been several times when my husband did not have his wallet with him and was detained until they could locate me (once I was miles away on a driving on a dirt road with friends) and verify his identity with many questions. They can make things very, very difficult for you so my advise is to either realize your responsibility is to submit to their authority or clear up whatever problem you've got about not wanting to reveal your identity truthfully to the police.