I have a 1998.5 24 valve ISB 5.9l. I seem to have a bad oil pressure sender, but Cummins has 2 senders on the engine. (Apparently - as I have only found 1 so far) - one for the ECU and one for the gauge.
Turns out the original oil sender for the gauge was a resister-type that sends an electronic signal of certain values to the gauge. It was fully analog, where the meter would move from low to high, according to the pressure it sensed.
The ECU sender is a digital sender, 1 or 0. either it has good pressure or it doesn't. +55 psi or nothing. Turns out the ECU will fall to a cripple mode if this one fails.
Now, Cummins in their infinite wisdom has chosen to switch the analog sender with the digital one. As you can guess, this creates basically an idiot light out of the gauge.
Why? I found an International part number for a sender that is similar to the original Cummins part number since Cummins no longer sells the old unit.
My Gauge is pegged to +120 when ignition is on. Im hesitant to start buying all theses senders with nor recourse. Cummins tells me to goto the idiot light option. i dont like that.
1. Old Cummins Sender: 3408428
2. New International Sender: 584051C2
3. New Cummins Sender/Sensor: 4076930
4. New Cummins Sensor Harness: 3164755 (req if using new sensor)
And extra numbers that might be useful:
4088390 - this seems to be an alternate Cummins part that will substitute the original, but Cummins doesn't cross-reference the ISB with this unit.
Also, Cummins part number 4921511 seems to be another OE replacement, but once again, Cummins doesn't cross it.
Reference: See here
, and here