Most likely your steering wheel is in the lock mode. If it is, then unlock it and your key will work properly.
It engages and disengages the lock that starts the vehicle. There are 2 parts to the switch. The ignition switch and the lock assembly.
If the Aerostar is not set for auto lock when the vehicle is put into gear, check the door lock, switch. Also check the lock relay and wiring for a possible short.
The first and cheepest thing to check is the fuses. located on the side of the dash by the passengers door, another is under the hood on top of the battery. The next would be lock switch.It is easily installed, no tools needed. The drivers side power switch is a master switch. This means that power feeds from the drivers lock switch to the passenger door. If your key fob will unlock and lock the doors but the switch will not I would replace the drivers door lock switch.
Depending on what year the car is the doors will automatically lock and what would cause them to unlock could be a faulty door latch There is a switch in the lock. probably that switch is broken in your car. If the inside lamp doesn't work when you open the door with that problem, that means the switch is broken.
More vehicle info would be helpful but most child safety lock switches are located in the area of the door latch. The door must be open to gain access to the switch.
The Anti-Lock brakes pulsate so the brakes do not lock up (anti) and cause the vehicle to side out.
There is a solinoid that actuates the lock mechanisim. Either you are not getting power to it due to faulty wiring or switch, or the solinoid is bad itself.
There is a small switch inside the steering column lock mechanism. When that switch fails it can cause the door alarm to chime. The chime is supposed to inform you that the key is still in the lock, but when that switch fails it can certainly cause the problem you described.
The ignition switch is immediately behind and attached to the ignition lock cylinder. The ignition lock cylinder is where you place the key to start your vehicle. If you are haveing problems with your vehicle not starting and or turning the key, more than likely you need to replace the ignition lock cylinder. It is common for these to go bad in GM vehicles.
the bcm will cause the door locks to lock and unlock by themself . the door lock master switch will cause wil cause the carvan not to start . first replace outside door handle key lock position switch part no#4687619. (new) you have 99% chance you'll get a bad one out junk yard. cost 50 bucks at the dealer. must replace the door lock it has switch too. at the cost $128.00.this will let you deactive the alarm system if lock are locking and unlocking you will have to change the bcm .Normally you must replace all the driver master door switches, sometimes hood switch,tailgate switch can causes the bcm to go bad as well in cause of no start disconnect the neg and the pos at battery let sit few hour to reset it self
replace master switch for door locks
a fuse, relay, bad ground or positive wire at switch or solenoid, etc.