I have a 2004 Mitsubishi Endeavor- the trunk will not open.?

I have tried using the door lock master on but trunk remains in the locked position. I have been told the Etacs module has to be replaced- this unit controls the doors, windows and trunk locks and is located by the fused box under the dash. My doors and windows all work. Has anyone had a similiar problem ? Does the Etacs module have to be replaced ? If yes does anyone know where I can find a used module ? New one run about $400. Thanks in advance.