Awhile back I posted wondering if a VTSS system that I didn't think I have could be causing a no start , and no 25 sec LP run that I was experiencing occasionally , I got no response .

 

This no start was happening it seemed after the bats were disconnected for a few days while doing other things to the truck , and then it would run again.

I had just replaced the ECM so I wondered if it was causing the problem , but the WTS was working ,LP 2 sec run with key to run worked and the cluster was also , when it ran it was fine , no codes , tach was not misbehaving

 

So it happened again after the truck had been sitting for a few days - bats where still connected

I started wondering - praying that maybe it was the crank pos sensor - truck is a 99 . Thinking it probably needs a reading from the sensor to activate the LP and somehow have the ECM able to start , from the starter spinning the motor

I did have a po 336 at one point a month ago ,cleared it and nothing more  , but I did  order a sensor from Genos  at that time .

 

I pulled the sensor , tested the 5 volt and ground , checked for resistance to ECM plug , and for short to ground , put in the crank pos sensor , and all was good ,   LP 25 sec  is back truck starts ,

 

Now I wonder if this is just coincidence or if that fixed it , I`d like to have faith in this truck again , not wonder if the ECM `s crapping out again

Does the ECM need input from the sensor to run - start , and for LP 25 sec starter bump

I`ve replaced probably 4 crank pos sensors in the life of the truck , usually it just makes the tack erratic  , maybe it went out completely this time ?

 

Sound like the crank pos sensor was the problem?

You do need a signal from the crank sensor for the truck to run. As far the 25 second lift pump run, I dont know. 

 

 

Beyond me, but I agree with the above and your thought process. 

Have you done the WT ground mod and checked your alternator to prevent future ecm failures. 

Yes did the ground mod , and have been running a denso hairpin alt since I put the 1st reman ECM in 2016 from Cummins, I check it once in awhile its real low AC 

That ECM I believe went out because I unknowingly left the seal off the plug on the CKP and it shorted out the 5 volt to sensor ground and sensor return , filled with water in the snow

 

I`d buy a ECM from Cummins again but they want 2800.00 for one now .

So this ECM is from ACS and I`d like to think its good ,Its a rebuilt that I paid core on .

 

I noticed that when it was running in between no start -no 25sec LP problems ,when it idled it would pulse a hundred  rpm up and down with the grids off , today after new CKP it idles steady

What worry's me about the ECM is  ,I sent in the one from Cummins , the one that I believe  shorted with water on the CKP connector in the snow , wanting to have an extra in the truck , sent it to ACS  they said they replaced quite a lot in it , but when I tried it , it still had codes locked in it , it wouldn't take a flash and it would not run the truck at all , I just sent it back under warranty a few days ago.

I don't know how they tested it good after repair and they missed all that .

 

That's why with the gremlins with this one I`m not sure I trust it , its defiantly  " caused " by the ECM  , still does it with the PCM and body module un plugged  , but  if the CKP wasn't sending any signal of crank movement to the ECM ?  I thought the cam pos sensor verified what the CKP input was ?    I wish I had some live scan that I could have confirmed that with,

 

Until I get a second ECM as a backup I don't trust the truck to go to far

 

 

7 hours ago, dieseled said:

What worry's me about the ECM is  ,I sent in the one from Cummins , the one that I believe  shorted with water on the CKP connector in the snow , wanting to have an extra in the truck , sent it to ACS  they said they replaced quite a lot in it , but when I tried it , it still had codes locked in it , it wouldn't take a flash and it would not run the truck at all , I just sent it back under warranty a few days ago.

I don't know how they tested it good after repair and they missed all that .

I'm not quite sure on water shortening out ecm, if wire torched positive from battery I could see how it could happen, but with water in a plug in would think it would just change resistance. @Mopar1973Man what do you think. 

My water in fuel plug is just hanging not plugged into anything, since I got rid of factory fuel filter and heater canister. Sometimes when it rains my water in fuel light will come on. I'm thinking I should fill it full of silicone for now.

My experience with ACS is neutral. I pushed a used ECM to have a spare for my own reasons. I sent it out to them to be programmed to my truck and have 3 cylinder idle enabled  (they call it cold idle I believe) got it back and installed to try it out, everything seemed to work fine for a couple of days, then out of nowhere driving down the road my tach went to zero. Got home scan for codes and got p1698 pcm not receiving bus. They told me it was my pump and I need to send it in for repair. I put my original ECM back in and all problems went away. Not sure how ECM will throw a code for PCM but that's what happened. So I have that ECM still sitting on the shelf and I don't know what to do with it. What's weird is truck ran fine for a few days, 3 cylinder idle work fine too. Maybe something in my wiring I'm just by switching ECM out problem goes away. I haven't tried switching back yet, if my current one ever goes bad I know that one works fine just no tach signal. What's weird is tack on dash didn't work but Quadzilla still showed RPM just fine. Idk I hate electrical Gremlins 

15 hours ago, dieseled said:

Does the ECM need input from the sensor to run - start , and for LP 25 sec starter bump

 

Yes. Without tach signal there is no way for the ECM to detect if the crank even moved. The cam sensor is only a single tooth TDC sensor. The starter bump looks for lack of movement or lack of engine starting to see if the prime cycle is to used.

41 minutes ago, Dieselfuture said:

What's weird is tack on dash didn't work but Quadzilla still showed RPM just fine.

 

CCD network issue. Quadzilla is directly hooked to the CANBus of the ECM. The Cluster is hooked to the CCD network so if the ECM isn't talking on the CCD Bus then the cluster doesn't read anything.

1 hour ago, Mopar1973Man said:

 

CCD network issue. Quadzilla is directly hooked to the CANBus of the ECM. The Cluster is hooked to the CCD network so if the ECM isn't talking on the CCD Bus then the cluster doesn't read anything.

So there is something in ecm that is not talking to ccd? I can't see how it's ccd issue as when I put different ecm in, no more problems. Basically if I sent ecm back to ACS I need to tell them to repair the part that is responsible for ccd communication?

The Cummins reman ECM I sent to ACS got back unfixed and is at ACS again shows CCD in my overhead console

 

The ACS reman in my truck now , Bob at ACS figures is not booting up half way , with no 25sec LP as one sign , he acted like it could not happen  , I`ve fired up the pins on the ECM plug and it engages my LP relay and starts the LP fine , no wireing issues , and checked all the other wiring I could think of before hoping it was the  CKP

 

When I got water in the CKP plug and damaged the Cummins reman ECM , it didn't just get wet , the plug socket on the CKP faces up and can fill with water if you can get enough spray to that area behind the starter , when it craped out I was in a few feet of snow , and out of town ,in CA , and then later while out of town at Cummins they pressure washed that side of the motor , because a 12 valve owner- employee  didn't know how to prime the 24 valve and dumped diesel all over the place , It ran extremely terrible after that and got towed home . 

7 minutes ago, Dieselfuture said:

So there is something in ecm that is not talking to ccd? I can't see how it's ccd issue as when I put different ecm in, no more problems. Basically if I sent ecm back to ACS I need to tell them to repair the part that is responsible for ccd communication?

 

Hopefully its been less than 6 months  , that's the length of time for full warranty from there to a year its a sliding scale

 

My Cummins reman thru a 1698 as one of the codes and was CCD

Switch to a different ECM and its fine  

4 hours ago, dieseled said:

Hopefully its been less than 6 months  , that's the length of time for full warranty from there to a year its a sliding scale

 

My Cummins reman thru a 1698 as one of the codes and was CCD

Switch to a different ECM and its fine  

It's been a year or so as when I sent them used ECM I told them it's a take out from a donor truck that supposedly ran. So their reply was, we'll it could be something with hardware and you only paid for updating software, need to send it in for repair for another $150. That's why it's still sitting there, because first response was bad pcm, then when I said if I put my other ecm in its fine, then it was back to, well you did get a used unknown condition ecm so it could be that. It's my fault for not putting it in the truck before I reprogrammed it just to see how it acts, now it's a shot in the dark. Everything works perfect except for tach dropping out randomly. I hope I'll never need it, if I do it still works, so whatever.