Code 2 means emergency vehicles are responding to an emergency, have their lights and sirens on, and are thus permitted to violate traffic rules.
Code 3 means that emergency vehicles are responding to a non-emergency, backup for a scene which is mostly under control, etc. But it is not urgent enough to warrant lights or sirens.
The terms you are using are not universal, and in the United States “Code 3” typically mean lights and siren, and “Code 2” typically means lights but no siren.
Code 3 means that emergency vehicles are responding to a non-emergency, backup for a scene which is mostly under control, etc. But it is not urgent enough to warrant lights or sirens.