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Engine ECM repair

GregD1

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Joined
Oct 6, 2013
Messages
221
Location
Tonopah, Az.
Occupation
Equipment for a paving contractor
Good idea or bad, you can get them repaired. We had a Freightliner crew truck with a Cat in it. It quit and we narrowed it down to the ECM. There is a place I think in Texas that fixes them. Don`t ask me the name of them, phone number or anything ele as I don`t remember it, but I do remember the cost was about 1/3 new and we were selling the truck anyhow. It ran fine when we put it back in and the new owner drove it off.
 

Randy88

Senior Member
Joined
Feb 2, 2009
Messages
2,149
Location
iowa
Not sure yet if this is somehow related, but the last I looked it, was about a week ago, hit the key this morning just to make sure it was still not going to start and now the new batteries are stone dead. We had this issue a couple years ago, nobody ever quite figured it out then either, it just kind of stopped doing it, as stupid as that sounds.

Boy the idea of someone else driving it away under its own power sure sounds great about now..............and its insured and everything. Oh well enough dreaming of what will never happen, back to reality and my current problems. I'll make a couple dozen calls and do some more testing and let you guys know about what I did or didn't find out before the weekend comes along.
 

02Dmax

Senior Member
Joined
Dec 4, 2007
Messages
687
Location
MO
First thing I'd do is unplug the harnesses at the back of the ECM. Check for power at the correct pins coming out of the harness. (I can probably find out what pins if you get me a serial number).

I always make sure the ECM has everything it needs to be operational before throwing one at it. You can have power at the fuses and still no power at the ECM if you've got a rubbed wire.

Does the check engine or stop engine light come on when you turn the key on?
 

Randy88

Senior Member
Joined
Feb 2, 2009
Messages
2,149
Location
iowa
I've been working on it all day, haven't accomplished much if anything, been on the phone more than not calling and asking anyone I can think of, both cummins and pete claim there is nothing between the batteries and ECM, I have power from the batteries to the first connection on the side of the engine, but lose it somewhere between there and the cab fuses. The wiring diagram I have only has the cab portion, nothing engine related is included, both pete and cummins have tried to send me the diagrams and they are completely illegible, they couldn't even read them to tell me what to look for or where.

The engine serial number is 34648536 according to pete, the serial number on the engine itself is illegible, the last of the truck vin is 312882, if anyone has a legible diagram for a L10e cummins, I'd appreciate it.

We've pulled the plug out of the ECM and we have nothing now for power there at all. Its possible the harness is rubbed through, but I'm thinking there has to a circuit breaker, in the wire from the battery to the fuse for the ECM, but I certainly can't find it if there is one, I have yet to take the dash completely apart looking, but its about to that point. As for a rubbed wire, that was the problem this morning down by the starter, a wire had rubbed the coating off against another ground wire and was a direct short, took some looking but I finally found it and figured out what happened, some new ends on the wires and that was cured.

As for at the plug on back of the ECM, I have nothing there at all on any of the power terminals, which is the reason I'm thinking a breaker is tripped somewhere, the main cab breaker is fine, and I don't think that ECM circuit should go anywhere through that, but I am curious as to why they didn't take the power for the ECM off the cab breaker, would have saved a lot of hassle going up the back of the engine and through the entire harness to get the power to the cab fuses for it and then back out again to the ECM.
 

lantraxco

Senior Member
Joined
Jan 1, 2009
Messages
7,704
Location
Elsewhen
It sounds to me like it would run, then you worked on the starter wiring and now it won't????? If that's the case you need to look carefully at what's connected to the batteries and starter and how, maybe the hot lead comes off the starter for the ECM and somebody accidentally got it hooked to the ground stud instead of the positive? Something along those lines.

Just a thought.
 

Randy88

Senior Member
Joined
Feb 2, 2009
Messages
2,149
Location
iowa
Lantraxco, That's what we've been thinking, same as everyone else, but we've checked and rechecked it many times, tracked the wires all down that lead to the starter and everything is hooked correctly, grounds go to the frame and engine and the hot wire for the cab circuit breaker go to the breaker, the starter switch wires go to where they should and the main frame wires are hooked hot as well, we've got them all to where the wiring diagrams say as well as what pete's reps tell me, they also claimed nothing that feeds the ECM comes off the starter anyhow, that comes directly from the battery. The connection we have tested for the ECM runs up above the starter on the back of the engine, just above the starter is where we tested those wires, they are hot there, then feed into the harness and are entwined in the wad of wires that go to the cab connection.

My first thought is still the same, despite what everyone says, I think there is a circuit breaker or fuse block in the cab somewhere that maybe someone added and when the starter was taken off, the batteries unhooked and removed, or the wires unhooked, someone shorted them and tripped the breaker or blew the fuse I have yet to find. To me this is the only thing that makes sense to explain what I'm not finding so far, I didn't take this apart and I have no idea how they did it, or what they may have omitted telling me or didn't notice as they did it, which really doesn't matter now anyhow.

I've been thinking about this during the night, the only thing I can think to try is to do a continuity test of the harness at the cab connection and carefully cut the harness covering to trace wires up to the cab. Then take the dash apart to access the harness in the cab and stick someone really small under the dash to hopefully find whatever it is I can't see.

Cummins wants about 4k for the ECM and Pete wants about 1200 bucks for each half of the harness.

I just can't believe since it ran before anything was done, the wires went bad or somehow got cut up behind the engine beyond where I tested them which is out of reach of anyone or anything, its got to be either GFS [green fuzzy sh@t] or a circuit tripped.

Once we get power back going to the ECM, we can start to troubleshoot that next.

I know I shouldn't be down on technology, and relive the glory years of day's gone by, but this is total BS, how much simpler things were when all you had to do was make sure it had fuel and good batteries in it, and a simple starter circuit to start it or jump it with a screw driver, an alternator to change the system and off we went. Makes me want to just go out and buy a much newer truck with an even more complicated electrical system on them to make my life easier, nicer far better reliability and to ease trouble shooting of problems, oh yea, and to make it cheaper to repair when things go wrong.
 

PNECAT

Well-Known Member
Joined
Nov 24, 2012
Messages
86
Location
MI
I'm having the same problem with my Kenworth T800 with a Detroit 60 series. Wiring and ecm problems. Sending the ecm out to a shop to get it tested for $60.00. Maybe you can do the same to verify the ecm is good or bad?
 

Randy88

Senior Member
Joined
Feb 2, 2009
Messages
2,149
Location
iowa
PNECAT, Where are you sending yours to have checked out.

The only thing I found this morning is, nothing of what I've been told is the case at all, we cut away the wiring harness and the wires coming from the battery box don't go to the cab first, they go the ECM first.

I'll have to wait till Monday and call cummins with the model and serial number to the ECM and see if I can get a wiring diagram for it.
 

lantraxco

Senior Member
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Jan 1, 2009
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7,704
Location
Elsewhen
Okay, just for clarification, you've traced the positive wires from the battery box all the way to the ECM connector?

Do they have power or not?

If not, where are the fuses, there HAS to be some kind of protection between the batteries and the ECM, possibly inline behind the battery box, along the frame, etc.?
 

Randy88

Senior Member
Joined
Feb 2, 2009
Messages
2,149
Location
iowa
Lantraxco, I took the harness from the batteries to the ECM out from inside the frame and out of the battery box, pulled it completely out and laid it out around the cab and re hooked it to the batteries, there is no fuse's in that section at all, no fusible link, nothing. I pulled the wires and unhooked the clamps/harness from the engine, I may have to pull the starter and ECM box off the truck, so I can see, right now I'm using an inspection mirror to follow the wires up to the ECM box, but I'm about sure they go to the box, not the cab, the other harness goes to the cab. It was dinner time so I haven't gotten back out there to test and finish following the wires up to the ECM or test it at the ECM.

I made a few calls yet this morning to ask WTF and all I was told one explanation is, someone cut the fuse's off the battery box end, as of yet, I don't know, another explanation is there also may be a circuit breaker in line that would be under/behind the ECM I can't see with the inspection mirror as of yet, I don't know for sure, I have a couple hours left to get everything exposed so I don't need a mirror to see with. Once the ECM is out, and I can get around back behind the engine to follow the wires into the head for the injectors and verify there is nothing around the corner, I don't feel anything by hand, but I want more verification nothing is behind the engine or bolted to the back of the ECM box and bracket somewhere I can't feel or see yet.
 

lantraxco

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Jan 1, 2009
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7,704
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Elsewhen
Sounds right, patiently following the electrical flow can be maddening on a modern vehicle, but sooner or later you should be able to confirm a fault or eliminate all but one or two possibilities. What you're doing is logical and methodical as opposed to the usual shotgun process.

:usa
 

02Dmax

Senior Member
Joined
Dec 4, 2007
Messages
687
Location
MO
You're headed the right direction now. Alot of Cummins had I line fuses hidden or tied up to the harness near the ECM.

IF you are able to verify 2 wires going from the batteries to the ECM and you still have no power at the harness plug, cut them off about 6 inches from the plug, hook some jumper wires to it and check for power again. If still no power it's about gotta be in the plug.

I know it's frustrating but don't over complicate it. ECM'S are bean counters, that's it.
 

Nige

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Jun 22, 2011
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G..G..G..Granville.........!! Fetch your cloth.
IF you are able to verify 2 wires going from the batteries to the ECM and you still have no power at the harness plug, cut them off about 6 inches from the plug, hook some jumper wires to it and check for power again. If still no power it's about gotta be in the plug.
Or better still, invest in a test lead kit for your multimeter with the "hypodermic needle-type" tips in it that allow you to measure for voltage or continuity through the insulation of the wires without having to cut anything. Fluke do a kit, it''s their reference TL81A and it''s saved my ass on a number of occasions.

If you now have the harness off and all connectors are accessible would there be any benefit in doing a continuity test in each & every wire to see if you have a case of electrons going in at one end but not coming out of the other..?
 

Randy88

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Feb 2, 2009
Messages
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iowa
I couldn't sleep so I went out to work on it again, finally came up with fuse's after tracking the harness far enough and doing enough testing, they were hid, someone bolted them to the backside of the mounting plate for the ECM, had to remove almost everything to get at them and they were blown, changed them and started sticking stuff back into place enough to see if it started, which it did, I'm not saying its fixed, still have to put it completely back together again and run it some to see if everything performs like it should, but it started and ran which left me speechless.

I guess if the starter was out and you'd look just right with an inspection mirror, you could see them....................who in the world came up with putting fuse's there, you wouldn't have been able to change them without removing everything though.

I now have to figure out how to bolt them somewhere we can get at or tie them somewhere handy, they are each on a pigtail end about six inches long that came out of the harness on the backside of the ECM bracket I couldn't see or feel, it wasn't until I started testing and taking the harness apart I found them.

Thanks for all the input everyone put into this project on my behalf I really appreciate it.
 

partsandservice

Senior Member
Joined
Feb 14, 2011
Messages
846
Location
Georgia
There seems to be no rhyme or reason for the placement of the ECM fuses esp with a Cummins. Once on a feller buncher that the alternator was not charging, after customer kept bringing alternators back claiming they were no good, I found the exciter wire to be the problem . I found a diode burnt out. Problem was it was inside the wrap of the wiring harness, I had to actually split the harness open with a razor knife to access and replace. Of course this diode only came with the wiring harness, but I installed a diode from a allied skidder. I then advised customer to replace harness as they are relatively inexpensive . He said he did not care as long as it was working.
 

lantraxco

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Jan 1, 2009
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Elsewhen
I'm going to put my swami hat on and guess someone accidentally reversed the battery cables or jumper cables and took out the fuses, not that it matters much at this point.

The evil conspiracy theory side of my brain tells me that's a great place for those fuses if you want to sell ECM's, and you can clean and resell the ECM you pull off to replace the fuses. Follow the money.

Well done! :drinkup
 

Randy88

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Feb 2, 2009
Messages
2,149
Location
iowa
Swami hat, that's a hoot, I have no doubt your right, but since I didn't take it apart, I can only guess and wonder..............but just like kids, nobody knows a thing about that, funny how that works.

Actually I'm speechless I figured it out, I never gave myself a ghost of a chance to ever troubleshoot anything computer or electrical related, to me those subjects are about like women, I'm pretty sure no matter what I do, say or try, I'm still clueless as to what exactly the signs are telling me, even when they talk and tell me what they want and mean, I can usually manage to botch something and someone ends up mad.
 

joelmartin

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Joined
Jun 30, 2010
Messages
115
Location
Hemet, California
Occupation
CEO AZ Technical,LLC
We disconnect the ECU terminal, the 12v power supply wires get probed by a simple harness.... 2 1156 taillight bulbs.. And the other end has a clip to connect to ground. If there's 12 v there with only one or 2 strands holding, it may show good continuity on meter, but the bulbs won't light very bright and then you'll know there's a problem with harness. Same with ground wire, except connect it to power to test if ground is intact. Just be sure you have the right circuits, or you could fry something
 

OCR

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Joined
Feb 21, 2008
Messages
1,195
Location
Montana
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Rancher/Farmer, Wildland Fire Fighter, State snowp
Actually I'm speechless I figured it out...
Lol... If that applied to me, I wouldn't be able to talk, ever... :D

Seriously, though... an exceptional bit of troubleshooting... Excellent!

Yup...
I couldn't sleep so I went out to work on it again...
Been there, done that too... ;)


Nige said:
I couldn't for a minute believe that the unswitched supply from the battery to the ECM would not pass through a fuse or circuit breaker first.

And why, why, wouldn't it be at, or as close to, the battery as possible?

Really makes no sense to me...


Again... good job, Randy... :thumbsup



OCR
 
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