Hey guys so hoping I can get some help with my no start issue.

1998.5 24v cummins manual I swaped into my chevy. First of all. About a month ago I was driving down the highway and my truck shut off. 
Died and left me stranded. Got it towed back to my shop in town and I was sure the injection pump died. So I swapped out the pump With a spare one I had and did not fix my no start issue. 
I have 20 psi lift pump pressure, good fully charged batterys so it cranks over fast. I did do the vp44 hot wire test and it starts. 
being this engine is a 98.5-00 that uses the cam and crank sensor. When I rebuilt the engine I replaced both of them so I know their good. I was leaning towards the ECM being no good. 
I swapped in a TEST. ECM that I have, it is from a 01. The truck fires right up! So should be the ECM right? 
I swapped in another 98.5 ECM, still no start. 
for shits I tried a 3rd 98.5 ECM. Still no start 

when I put the 01 ECM in. Fires right up. 
I can read codes off of the obd2 plug I have wired in the truck. And clean them. 
I do have a p1689 code.

 

WHAT I WANNA KNOW IS:

-what is different between the 98.5-00 and 01/02 ECM that would allow my truck to run. 
- if in fact it is a can bus issue causing the no start. How would it start with the 01 ECM and not that 98.5.

 

any input would be awesome! Thank you 

They changed sometime to a cam only sensor. For that you need the cam gear with the fine tooth trigger wheel on it. The older sub gen on the 99 uses a cam gear with only one notch on the back and the tooth wheel on the crank. Seem dodge was worried about run away trucks like Toyota. So the ECM and vp and APPS have a complicated system of checks and multiple shutdown methods. First the CAN bus can command it to stop. Second there is a shutdown wire VP pin 5 LT blue/red 12volts kills it 0 volts is run you can cut it and let it hang leave enough wire to reconnect later it may throw a code. Third the ECM deenergizes the fuel system relay shutting off power to the VP pin 7 red/lt green. The VP won't  rev up unless the idle valve signal VP pin 4 goes to 0. When it sees that, it changes a bit in its CAN message reply back to the ECM this is a cross check if things mess up you can get a dead pedal or a complete shutdown. Make sure you have the right cam gear and sensor(s) to match the ECM.

Great work is right. Best to keep the match ECM for that block. Makes it worse when retro fits are done without the PCM because now you can't read codes. It required to have the PCM to read error codes. 

 

 

Okay sorry for the late reply, been swamped with work lately. Finally time to get back to the project toy. Anyhow. 
This isb platform I am talking about has a full rebuild. The cam gear is correct for the year of engine 98.5-00. 
it has both new cam and crank sensors from that year of dodge as well. So I know I’m not messing around with unknown parts. 
The ECM for this block kicked the bucket a year ago. So I found a good used one, for the same style engine out of another truck. ( confirmed by cummins quick serve using each ESN.) 

I can read engine related code, and clear them with my scan tool. However, without the pcm I cannot live data stream with my scan tool.

 

all that said, 

 

with a (non crank sensing ECM. Plugged in.)

the truck starts instantly (01-/02ecm).

MY SPARE TEST ECM 

 

with a ( crank and cam sensing ECM. No start) 

(98.5-00 ECM) THE CORRECT ECM 

 

fair to say the crank sensing circuit is not working correctly to sync cam and crank to start the engine? 

i know my ground and 5v ref circuits are good. So I assumed it would in fact be a can bus no start issue. 
 

Any more input would be awesome. 
thanks again 

Did you drive the truck with the 01/02 ECM? Did it run at full potential or in a default limp mode. Seems it would not like the signal from an incorrect cam gear. Anyway, Check the signal coming out of the crank sensor with a good meter or scope. It should be a 5 volt square wave while the engine is cranked. Maybe the older ECM came from a truck with a factory security system

i'm not sure how those work could be it needs something from the PCM.