This Preliminary Information communication provides information to the technician the steps needed to diagnose and repair the vehicles that may have unwanted or phantom phone calls. Technician will need to determine what type of call the customer is having that is unwanted. The vehicle may receive an incoming call just like any other phone. Typically the customer will hear the phone ringing in the vehicle. This scenario also includes incoming Bluetooth calls. One type of unwanted call can be made if the key pad is faulty the OnStar system will try to make a blue button call for shorted voltage in the circuits. The OnStar module could have an internal fault and produce a "Phone Unavailable" audio message also it may have a Diagnostic Trouble Code U1500 or B1000. Refer to diagnostics for the Diagnostic Trouble Code making sure to follow any applicable Bulletins or Preliminary Information sheets. A "Ready" or "OnStar ready" audio message heard while driving. In some cases it has been found that the customer is inadvertently pressing the ?push to talk? button on the steering wheel controls. On rare occasions, other issues in the steering column or Steering Wheel Control system may induce this concern.