This Preliminary Information communication provides information to the technician about vehicles that have an OnStar system that will not power up. Technician should turn off the ignition and cancel retained accessory power. After the vehicle has powered down remove power to the OnStar module for five minutes. After the power has been removed for five minutes, if the OnStar system is working release the vehicle. If the OnStar system is still inoperative continue with published Service Information diagnostics.