after it dies do you have spark?
That engine does use 2 crank sensors a 24x in the block reads off the crank, and a 3x that reads off the trigger on the balance. the computer uses this sensor at engine speeds above about 1800-2000rpm. I have seen the crank sensor at the front fail many times and never leave a code.
Also does it die like you shut off the key or does it die like you dumped the clutch in a stick shift car?