Possibly a failing CPS (Crank Position Sensor).
I would go to AutoZone and see if they can scan the codes for you.
The 1693 is a companion code. This means there is a "Soft Code" stored in the computer (either PCM or ECM) that can not be displayed with the key on/off method.
This code indicates that other codes have been set. By it self, it means nothing.
A crank sensor is only about $80 (from Cummins) and is relatively easy to change. See if you can find out the codes. Let us know, we will be more than glad to help.
-Rich