I have found that the tool change solenoids or the solenoid cable shorts out. You have a solenoid for pre-charge and one at the Tool release piston. If your machine has a gearbox then you have a solenoide behind the mounting bracket for the Z axis cable track. On the I/o board you will see usually on the lower right hand side of the board a connection labeled something like "solenoid" or head Solenoids. Unplug this and see if the alarm goes away. Also another common cause is a worklight. Unplug the worklight cable.