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Discussion Starter #1
i got a 2000 3/4 ton with the cummins, vp44 stock lift pump.. truck starts horrible, sometimes not at all, and i found it had a bad alternator, replaced alternator and my original condition exists still.
the truck will idle perfectly smooth at 16 to 18 volts with alternator unhooked battery charger on high. hook the alternator up so it limits the voltage to nothing above 15 and it skips like a mother, and it won't rev up with rpm gains of over 300 rpm without the charger it has a dead pedal, any help on if this is ECM related or is there something in the injector pump thats gone bad but will let it run smooth with extra voltage?
 

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im not big into the electrical part of th truck but im sure someone one here will be able to help you out. :thumbsup:
 

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I would start with testing batteries then go on to ground cables. Then go to power cables.
You can also check for codes my doing the key trick. If your not familiar with it turn the key to the run position and back off on the 3rd time leave it in the on position and the odometer will tell you codes if any.
 

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ok i'm posting off my phone. there is a thread here where you can do an apps reset. let me figure how to copy and paste.
 

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clean your battery cables. try to get some codes too. can't copy so go to tech in the heading then 98.5-00 maintnence then APPS reset
 

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Discussion Starter #6
i will try the apps reset, all cables are good, two brand new batteries i put in with the alternator, only code is shows is a p 1693 and i was told its an ecm fault code?
 

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Discussion Starter #7
may i also add to this that when hooked up to my snap on modis scan tool the ECM will not communicate with the scan tool, but it does power it up to turn it on
 

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that does sound odd. i had a simular problem with that before. our case the cable was messed up...lol that's hard to say though.
 

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Discussion Starter #9
that does sound odd. i had a simular problem with that before. our case the cable was messed up...lol that's hard to say though.
well the modis is self powered so i didn't know if the power side of that plug was working or not so i tried my old snap on brick, it powers on the unit but doesn't read the ECM but both work on my 2000 s 10.

the whole scenario has smoke coming out of my ears, it idles near perfect at 18 volts, probably 750 rpm, throttle it up it raises maybe 200 rpm then starts to spit and spudder and miss until you let out of it. and it won't idle smoothly with the alternator hooked up running 14 volts??? i'm about ready to take it to a shop and say here fix this but i know the first thing they'll do is throw a new VP on it and if it doesn't fix the problem there goes 1500$
 

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I take it you have, checked and repaired all codes any code once it gets to 255 counts will cause a problem. first is to check codes, If you have a manual there are 13 things to check before the VP44, Fuel, coolant level, and grounds are the ones I would look at first, I can tell you for sure running it at 18 volts will destroy the ECM and a lot of other sensors.
 

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I take it you have, checked and repaired all codes any code once it gets to 255 counts will cause a problem. first is to check codes, If you have a manual there are 13 things to check before the VP44, Fuel, coolant level, and grounds are the ones I would look at first, I can tell you for sure running it at 18 volts will destroy the ECM and a lot of other sensors.
well like i said i can't get any scan tools to communicate with it, but when i cycle the ignition the only code i get is a p1693, not even listed in the manual for the truck. when it is running at 18 volts it will rev up slightly, but with the alternator hooked up running at 14.4 volts all it will do is studder shudder and spit, it won't start and come to an idle without a battery charger on high until the alternator kicks up.
 

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P1693 is a companion code set by the PCM indicating the presence of codes in another module, I'm betting in this case the ECM. I believe your problem is going to be a bad ground to the ECM, or a failed ECM.
 

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P1693 is a companion code set by the PCM indicating the presence of codes in another module, I'm betting in this case the ECM. I believe your problem is going to be a bad ground to the ECM, or a failed ECM.
thats what i'm hoping for, people keep saying its the IP but, when it gets the 18 volts it idles perfectly so i don't understand why it would be the IP? im going to check the ground wires tomorrow
 

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does the ECM on these trucks ground through its mounting bolts or does it have a ground wire coming off its main plug? i checked all the grounds i can find and all seem to be good, i pulled the ecm off and it looks to be in rough shape, good ol new england salt but that doesn't mean much, just want to check all my options before replacing it, also is there any way to test it to see if its any good?
 

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thats what i'm hoping for, people keep saying its the IP but, when it gets the 18 volts it idles perfectly so i don't understand why it would be the IP? im going to check the ground wires tomorrow
You know, I just got thinking. (Yea, I know, it scares me too...) Check fuel pressure at normal voltage and at 18v. Maybe the IP is getting weak and the increase in voltage is speeding it up enough to help.
does the ECM on these trucks ground through its mounting bolts or does it have a ground wire coming off its main plug? i checked all the grounds i can find and all seem to be good, i pulled the ecm off and it looks to be in rough shape, good ol new england salt but that doesn't mean much, just want to check all my options before replacing it, also is there any way to test it to see if its any good?
I think you can take it in to Cummins and have it tested. I'm not sure about the grounds, you'll have to find a schematic. I think Mopar1973Man has one on his site.
 

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well like i said i can't get any scan tools to communicate with it, but when i cycle the ignition the only code i get is a p1693, not even listed in the manual for the truck. when it is running at 18 volts it will rev up slightly, but with the alternator hooked up running at 14.4 volts all it will do is studder shudder and spit, it won't start and come to an idle without a battery charger on high until the alternator kicks up.

You should see 2 P Done's and P_PCU and P_ECU...

P1693 means there is MORE codes present in the other computer which happens to be the one you cancelled out (P_ECU)...:doh:

Go here and watch the video...
OBD II Error Codes
 
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