New ECM and now No start....Please Help!

[LmtvPR]

Hey Guys, So I got a LMTV M1078A1 with Cat3126. the truck was running perfectly then I washed it and when parked after running fine for 30+ minutes I disconnected the battery and went to start 4 days later and the ECM was gone. I got the ECM repaired and put back in the truck and now it will not start. I have replaced the ICP valve and sensor but still nothing. I didn't mess with anything other then getting the ECM repaired after losing power so Im lost to what it could be. I have fully charged batteries and checked all connections. Please let me know if there is something else I can check.

 

[Keith Knight]

My ECM failed me as well years ago. At that time I couldn’t find anyone that I trusted to do the repair so I bit the bullet and purchased a new one from CAT and then it was on them to program it at they even upped my horse power to 330. Any ways it might just be they didn’t fully repair your ECM?
Another thing I like about doing it through CAT is my data is saved on there system and can be used at any cat service center.

 

[LmtvPR]

Thanks for the info, I have called my local cat dealer in Puerto Rico but they want 8 hours @ $125 to trouble shoot. I was thinking the ECM could have an issue as this is my second one from Diesel ECM Exchange. The first unit only lasted a week and they said a coil and capacitor went bad inside. My first unit had a generic file for the truck but upped HP to 325. I guess they called Cat the second time and got a new file per my serial number and that is what was loaded in the new ECM with the HP add but now it won't start. I was going to try to replace the Cam Position sensors next.

 

[wheelspinner]

Thanks for the info, I have called my local cat dealer in Puerto Rico but they want 8 hours @ $125 to trouble shoot. I was thinking the ECM could have an issue as this is my second one from Diesel ECM Exchange. The first unit only lasted a week and they said a coil and capacitor went bad inside. My first unit had a generic file for the truck but upped HP to 325. I guess they called Cat the second time and got a new file per my serial number and that is what was loaded in the new ECM with the HP add but now it won't start. I was going to try to replace the Cam Position sensors next.

Any chance to swap a known hood ECM in?
May have to find a way to plug in and “see” what’s really going on.

 

[LmtvPR]

Any chance to swap a known hood ECM in?
May have to find a way to plug in and “see” what’s really going on.

No I don't have access to another ECM. Being in Puerto Rico I have limited resources. I just may have to bite the bullet and pay to have it scanned.

 

[wheelspinner]

No I don't have access to another ECM. Being in Puerto Rico I have limited resources. I just may have to bite the bullet and pay to have it scanned.

Give this a look

 

[LmtvPR]

Give this a look

I saw that video last night and considering it just dont want to spend that kind of money but may have too.

 

[wheelspinner]

I saw that video last night and considering it just dont want to spend that kind of money but may have too.

One and done

 

[LmtvPR]

UPDATE!... I finally was able to get the truck scanned today and its showing "Short" on all 6 injectors. All other parameters are reading perfect on the truck so my mechanic believes the ECM is bad, so I removed and will be sending to Diesel ECM exchange on Monday for them to inspect and repair.

 

[LmtvPR]

Has anyone had this issue before or know the cause so I can try to prevent it in the future?

 

[Ronmar]

So what is the measured resistance of your injectors? Are they indeed shorted? I am not specifically familliar with the cat HEUI ECM, but I seem to recall reading about configuring/matching injector settings. If the ECU was multi purpose it may be able to drive different types of injectors for different applications. If it was set for a different type it may see yours as open or shorted as it is looking for different feedback from different injector types.

Did they repair your ECU or send you a different/remanufactured ECU? I have heard of a particular flaw with these that their internal battery fails over time and when they loose external power, they then drop their programming and cease to function. That sounds like what happened to you initially.

I believe Cat references everything to engine serial number, so that would be required for someone to re-load the same tune into a replacement ECU, that or someone with enough experience to set one up from scratch in the field…

 

[LmtvPR]

My first ecm I belive had a battery loss of power which caused failure. my second ecm had the same but also the mother board was fried possibly from water when i washed the engine but the truck did run after. now its only injectors "short" they said this is a new file from the previous computer that came directly from cat where the other file was a more generic file they said. i want to test the ecm power supply pins but can't find any info on what pins to ohm to see if there is a short. also should my battery have a direct chassis ground? i have 4 batteries set up for 24v that go to a factory disconnect switch but im not seeing anything to ground at or near the battery box.

 

[Ronmar]

The main truck ground is a strap between the starter negative terminal and the left side frame rail…, so it goes from battery neg terminals(furthest from the frame) to the starter neg terminal via large gauge cable, then there via a ground strap to the frame. The A0 had a instrument shunt in that large gauge ground wire to measure overall current flow into and out of the batteries with the STE test equipment. They did away with the shunt on the A1 but kept the same overall wiring plan… You should be able to measure from bare metal anywhere on the frame to the + terminals on the batteries and see 12 or 24V…

google 3126 ECU wiring, you should find all sorts of drawings showing you the ECU connector pinouts…

 

[Ronmar]

oops, double tap…

 

[LmtvPR]

ok thanks for that info. i have that strap on the alt so I'm sure all is good. I'm going to check for shorts tomorrow just to verify nothing is causing a draw when all power is off.

 

[Ronmar]

Take a good look at the strap on the starter, it is the most important one…

 

[Keith Knight]

Has anyone purchased that laptop and data port from kt3406e? I’m seriously considering it. If it is everything he says it is it would be a great tool for someone like me that does all of my own repairs.

 

[m-35tom]

Has anyone purchased that laptop and data port from kt3406e? I’m seriously considering it. If it is everything he says it is it would be a great tool for someone like me that does all of my own repairs.
[/QUOUT]
I purchased the adaptor for my A1R and found software online so I cam do anything. Engine ECU, trans control, speedometer, ABS etc. About $500.

 

[wheelspinner]

Tom, can you help me find the software?

 

[m-35tom]

Been a long time since I got all that but I think you need Diagnostic Tool 317-7485 For CAT Equipment and the adapter for trucks to have the plugs that fit LMTVs. Then PM me for the software.