This is Dodge stuff but may help, the ecu loc should be the same. Geno's has been very helpfull, call them.
ECM details for 1998-2002 Dodge Ram trucks with 24 Valve Cummins diesel engine
" Engine RPM and timing are derived from the Crankshaft Position Sensor (CKP) on 1998-2000 models"
Our 5.9 was throwing codes and our ScangaugeD read them. We had Low volts, erratic rpm signal and 1 other. Cleaning and applying dielectric grease to the multi-pin connector solved the low volt issue and a new CKP solved the rpm signal. HTH. A SGD is a great tool and not expensive.
Here's some of my thread on this; I replaced the crank sensor today.
Your bus will probably be a bit different.
Disconnect neg at batt.
Disconnect neg. connections at buss bar near starter.
Loosen or remove starter, 10mm 12 pt. is required.
If not removed, pry starter away from sensor and remove sensor from block.
Unplug sensor and re-plug new one.
Replace all that was loosened or removed.
I needed a 10mm 12pt. box ratchet to remove the top starter bolt. There are 3.
I had to unplug the multi-pin connector and move the dipstick tube to see the bolt.
Next time I can do this in a couple hours, this was the first time and it took me all day at a 72 y/o's pace.
Road test to come.
This bus would produce a code after being fully warmed, shut off, then re-started. The code would show as SES after 1/2 hr. or so of running FULLY warmed. The engine would de-rate to lower power and the idle had a nasty surge. It would clear after a few seconds to a few minutes., usually instantly via the Scangauge. The tach never showed any rpm fluctuations.