Can a passenger in a lawfully stopped vehicle refuse to identify him/herself?

Yes. LE has the right to order all occupants from the vehicle, and while the driver is required to present identification, the passengers cannot be compelled to do so unless LE has a separate justification for that request, such as seeing a crime being committed (contraband in plain sight), passenger interferes with LE contact with driver, passenger is a known associate of driver’s criminal enterprise, etc. See United States v. Landeros (9th Cir. 2019) 913 F.3d 862. Once LE has that reasonable suspicion for the passenger, a detention is legally allowed and passenger must present ID. Also, if LE has an articulable concern that the passenger might be armed, a Terry frisk can be performed.