| Author |
 Topic  |
|
|
td083
Senior Member
195 Posts |
 Posted - 07/21/2017 : 05:47:38 AM
|
--Just curious if anyone has ran across a bad ecm in a maxxforce dt
--bus came in no gauge operation all gauges don't sweep or move but all lights do self test in cluster .the center display shows a electrical fault message
--I cant communicate with the bus with scanner ***until ecm is unplugged then shows its getting info from other cpu's the tcm /abs and body all show counts of communication
--I did check resistance in can system its 120 ohms where ever you check it suppose to be 60 ohms**but both 120ohm resistors were checked good
--I did confirm on a sister bus and it was 60 ohms just figuring if it were a wire issue why odd its 120 and theres 120 ohm resisters in the circuit would figure would be something higher if wiring were at fault
--when I unplugged all other cpu no communication would occure only when ecm was unplugged . already checked all fuses and relays also no 2.5v on can wires ran through troubleshooting states bad transistor could cause this inside one of the modules , when I removed the ecm and checked the internal resistance of the transistor it failed was way lower than it should be
---even though its all pointing me to the ecm just hesistant one its on national backorder no one stocks it anywhere (which to me can mean it doesn't go bad and ya miss diagnosed it ) and two the ecm is 2500$
---whats your thoughts ?
--
|
|
|
RonF
Top Member
867 Posts |
Posted - 07/21/2017 : 06:04:36 AM
|
| Typically when you get the "Electrical Fault" message and the problems you are describing it is not the ECM but the "Clean" power circuit. That is the wiring from the batteries to the ECM relay. Look in your battery box at the harness with the 3 fuses. Pull each fuse and look for discoloration in the sockets and pins or melted plastic. Check the 3 wire connector for the same issue. Go up to the fire wall and find the ECM power relay and look at the connector for burnt sockets or melted plastic. Also between the battery and the relay there may be a connector or two, check these sockets and pins as well for the same thing and replace accordingly. I have yet to replace and ECM for this fault. |
US Army retired CMBT |
 |
|
|
td083
Senior Member
195 Posts |
Posted - 07/21/2017 : 07:36:16 AM
|
Yes I agree , my first check was the battery box all the fuses and checking pins then checked voltage at ecm relay ,
--I just checked power and ground to connector 6020 (at the ecm ) from the clean power circuit found had battery voltage and ground at all pins that were fed by clean power circuit
--*******one important note I forgot to add was I was able to link up to abs system on Bendix and also **had a dtc for a j1939 can interruption as well
---yea trust me I don't wana throw a ecm that obviously never goes bad on a bus for 2500$ but everything I'm checking is leading me there ,
--I will also add the bus starts and runs ok just gauge operation inop which makes sense seeing the cluster gets info off the 1939 can wires according do can diagram |
Edited by - td083 on 07/21/2017 07:37:00 AM |
|
|
|
RonF
Top Member
867 Posts |
Posted - 07/21/2017 : 09:56:18 AM
|
Yeah if the bus starts then it sure wouldn't be a problem in the clean power circuit. Try swapping ECM's from a good bus and see if the problem goes away. Install the bad one on a good one and see if the problem follows.
Have you pulled apart all of the J1939 connectors and reconnected them? |
US Army retired CMBT |
|
|
|
td083
Senior Member
195 Posts |
Posted - 07/21/2017 : 10:55:28 AM
|
Yea true everytime ive had a issue with that clean pwr circuit it crank no start but thought I better check in case low voltage or some is dropped somewhere along it I know sometimes the connectors are poor fitting . Just want to make sure I don't skip over an easy check that I know is such problem area ,
---yea every module the ecm--tcm--body and abs have all been disconnected and while each was out of the circuit I checked for communication on the scanner only when the ecm was disconnected did the other modules pop up showing can communication of some kind
--yea may swap one on Monday and see what happens Thanks |
|
|
|
drp53188
Senior Member
89 Posts |
Posted - 07/24/2017 : 10:12:05 AM
|
Do you have diamond logic builder??
What codes are in the body control module ??
if not check for pushed out pins on the BCM.
If you have DBL go in and you can sweep the gauges to see if you have an input or output wiring problem. |
|
|
|
slippert
Top Member
USA
630 Posts |
Posted - 07/25/2017 : 09:47:03 AM
|
If you have OnCommand look up Iknow article IK0800080 tells all about diagnosing the 1939, the symptoms you describe sound a lot like the same... there is also a 11 by 17 troubleshooting card available from dealer that goes thru same steps.... if you don't already have these...?
I am currently battling a similar issue on a 2013 bus, throwing lots of active codes(loss of ecm, tcm, abs comm and a multitude of others) intermittently.... bus stalls and will not restart when codes go active......wait for 20-45 seconds with key on and bus starts and runs fine.....may go 5 miles or 500 miles before next event happens
So far my clean power is fine.... at point of disconnecting one ecm at a time to see if it will stop problem.....that is if i can get it to last long enough to track down issue |
Edited by - slippert on 07/25/2017 09:57:54 AM |
|
|
|
td83
Senior Member
83 Posts |
Posted - 07/25/2017 : 12:43:06 PM
|
Thanks for the info all , havent been back at this one yet , where im planning to go is like drp53188 stated the dlb could be of some help and to be honest i use isis daily but havent used dlb yet other than training so gonna see if that gives me more info .
other than that going to check the transceiver pins on a sister bus ecm if that gives me the correct reading ***according to my can system diag sheet*** il replace the one on my bus , because mine is giving a reading indicating the ecm is bad .
Got the go ahead to order the ecm just have hesitation **one the bus starts and runs fine dash just states electrical fault and gauges are inop this doesnt sit right with me i would feel a lot better about condeming the ecm if it was a crank no start
***the other is my resistance readings are odd between the can wires should be 60 ohms mine are all 120 and i compared to sister bus to verify
And thanks slippert il check that article out .
|
|
|
|
td083
Senior Member
195 Posts |
Posted - 07/27/2017 : 08:46:07 AM
|
| ---Just an update I swapped out a known good ecm, body ecu, and gauge assy still has same issue stating electrical fault in dash starts and runs |
|
|
|
td083
Senior Member
195 Posts |
Posted - 07/31/2017 : 07:22:55 AM
|
--Just an update sent this one out to dealer, I suspect a harness issue from outside the bus
--found out my resistance reading when checking the can wires together was good but when checking the wires individually to ground was bad indicating short to ground checked around as much as I could , couldn't locate , problem area and the inside the bus readings were not correct either when compared to 2 sister buses . |
Edited by - td083 on 07/31/2017 1:26:21 PM |
|
|
|
td083
Senior Member
195 Posts |
Posted - 08/07/2017 : 06:21:40 AM
|
---Just got information from the dealer , they are suspecting multiple module failure
stating looks like bus (which did look like was sitting under a tree a while) was either struck by lightning or jump started with to high of voltage .
--Basically they said they were only able to communicate once everything was unplugged (don't know what one yet was left connected ) yet . I gotta say I feel a little vindicated this one had my headspinning for sure . |
|
|
|
td083
Senior Member
195 Posts |
Posted - 08/24/2017 : 08:25:17 AM
|
| We got this one back from the dealer they replaced EVERY module on the bus , likely struck by lightning . |
|
|
|
bluebirdvision
Top Member
USA
1081 Posts |
|
| |
Topic |
|
07 epa Maxxforce dt -Faulty ecm ??
