Just finished going thru the ups and downs with my oil guage on the 2001. Pressure went to 90 and then zero and finally stayed at zero. Dealer said as long as the oil level was at normal to drive it into the dealer (70 miles).
1. Reflashed as per D C. Went home and stayed at 40. Shut it
off and 45 minutes later turned the ignition on and bingo 90lbs
and engine not running!!!!!
2. Returned to dealer to have the oil pressure sending unit
changed and no problem since.
Do a search as there are prior posts on this subject including Cummins prices vs Dealer prices on the sending unit.