Sounds like you have 2 issues.
First, the grid heaters, check to see that both of them are plugged in. I've only seen the code when one of the two smaller wires comes disconnected. If they are, then continue with the usual tests (search the forum for that, several recently).
The second issue sounds like you may have a minor fuel leak that is letting air get into the system. The only time a Cummins dies like that with no codes is a lack of fuel, maybe a flaky shutdown relay, or part of that electrical circuit.
That P0602 code is something to worry about though.
SYMPTOM
P-0602 ECM FUELING CALIBRATION ERROR (OBD II)
WHEN MONITORED
Ignition on
SET CONDITION
If any parameter is out of range for 1 second , a DTC is stored and the MIL is illuminated.
POSSIBLE CAUSES
Specific good trip counter not equal to 0
Engine control module defective
It's a two step trouble shooting tree,