2004 chevy Malibu won't shut off

I have a chevy Malibu classic when I take the key out the car is still running and drivable. Sometimes the engine shuts off when I turn it off but the fan and radio is still running does anyone know what's wrong so I can put it in the shop? I don't want to take it to the shop not knowing what's wrong with it and having to pay an arm and a leg. I want to know what's wrong so I can price it before I put it in the shop

There are several possibilities. One is a failing ignition switch, where the switch contacts do not open as designed. Another is a possible problem is with the accessory power control (RAP) system. Another possibility is damage to the wire harness, something which has plagued more and more vehicles as a result of increasing complexity and downsizing components for material conservation.

Someone will have to invest time to diagnose the problem to determine what is at fault, and that is where the expense of repair is created.