03 Sante Fe will not crank over, but will start only once if battery disconntected
 

I have a 2003 Hyundai Sante Fe and motor would randomly not crank over. This happened on 3-4 occasions, I would click lock/unlock buttons numerous times, move shifter from park, drive, neutral and sometimes it would start after some time. Now, it will not crank at all, nothing seems to work except when I disconnect battery and leave for several hours, then reconnect battery, but it will start only once. I checked start relay, good, checked connections to starter, good, checked battery ground wires, good. I thought the power door locks were affecting car security and not letting car start, but I changed the front passenger lock actuator, which was the only one not working. I replaced transaxle switch, but still does not crank. I checked/swapped start relay, b/a relay, ignition switch wires, all appear good. My next step is to replace ECM, but I don't want to put out the money as it is an expensive proposition for process of elimination. Please, does anyone have any suggestions?

I would check for codes Advance Auto and Auto Zone will do this for free. The crankshaft position sensor will go bad and cause these types of problems. The 3.5L requires you to remove the timing belt to replace. If the starter won't turn over try tapping the starter with a hammer if it starts replace. Use a 12v test light and check for power to solenoid. If no power check ignition switch a $20.00 item on end of key. Purchase a Haynes manual and look at wiring diagrams. Google alldatadiy a years subscription costs $24.95 needed to diagnose. Check neutral safety switch or clutch switch.