Q: Car want start unless boosted, alternator good and battery good, while boosted the car crank in the key off position.

You should request a starter circuit diagnostic to get this resolved. If you want to attempt to diagnose it yourself, first perform a load test on the battery just to be sure that the battery is not an issue. If the battery happens to be discharged when you attempt that test, suspect a parasitic current draw in your car’s electrical system which is depleting the battery while the car is off, thus making it impossible to start the car at next use. If the battery does pass a load test and yet there is no starter operation with the key held in the "start" position, the procedure is to test for power and voltage drops to the starter motor/solenoid. If there is no power, or a large voltage drop is measured, then the electrical circuit supplying the motor has a fault. That circuit begins at the battery and includes grounds, wiring (some of which is very heavy cabling), fuses, relays, the ignition switch, neutral start switch, and terminations. Basically, with a fully charged battery, and with the key held in the "start" position, the starter is either getting power or it isn’t. With the key in the "start" position, if the starter motor is getting power but the starter doesn’t work, then the starter is condemned and replaced. Note that starters can and sometimes do develop intermittent faults due to bad spots on the armature. The bottom line is if there is battery voltage to the starter (and no excessive voltage drop) and yet the starter doesn’t work, it’s dead. If you want these steps performed by a certified Mechanic, dispatched by YourMechanic right to your location, please request a starter circuit diagnostic and the responding certified mechanic will get this taken care of for you.

With regard to the power steering issue, in 2014 GM recalled many vehicles, including your model, to address problems with the power steering system. Depending on the vehicle GM was to replace either the power steering motor, the steering column, the power steering motor control unit or a combination of the steering column and the power steering motor control unit. You should check to see if the required repairs were made on your vehicle but, if not, whether you are still eligible. If you are not covered for the repairs, YourMechanic will diagnose and resolve the issue for you if you request a power steering warning light diagnostic. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.