94 Buick lasabre? trying to read the diagnostic codes but the OBD2 displays error help?

[Carolyn m]

the buick keeps like stuttering and then the car dies but i can just start it back up again. we are trying to find out why its doing that and have no idea because our OBD2 display error and can not connect( what other tool can use so it can read the diagnostic codes) we have changed the spark plugs put new oil in cleaned the throttle body.( this buick hasn't been driven much over the past years ) can anyone help or tell me why it keeps jolting then stopping please and thanks