can the ecm keep my truck from cranking

NO. but a ten year old battery an offer reduced voltage and confuse this electronic brain~ darned it, my 93 pickup had NO buzzer...at all, lights or anything...that damned kid who never did any oil changes, jerked out the door switch and buzzer...still trying to figure out where that is once I'm able to find another buzzer...have left my lights on too many times~ a big Hunkin' stereo that was this man's objective in life~ nothing else mattered...so tragically have these issues to deal with daily~

First, have you tested the battery ? if the battery & cable connections are good, check the clutch switch, it prevents the engine from cranking unless the clutch pedal is depressed. Also, it could be just a worn out starter & solenoid. Need more info for an informed answer.