Car's been down for almost a month and the mechanics i bring my car to cant find out whats wrong with it... What can cause the car to shut off after driving and not be able to turn on after? Check engine light came on but the computer is giving out an error? What can cause the ECU to be unreadable? Can it be the main relay?

 

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+1. Car drives for miles and you stop for gas and shut it off and it won't turn back on? Or car drives and randomly shuts off and won't turn back on?, etc. Setup?