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bullshark102
New Member
5 Posts |
 Posted - 09/15/2015 : 12:49:57 PM
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| I am currently working on a 2006 BlueBird All American with front mounted C7 CAT and equipped with Bendix Air. The abs light comes on during initial startup just as its supposed to then goes off. The only thing that hints to the problem is in the message center under the odometer it reads "ABS COMM FAIL". I have checked any relevant fuses and relays, the plugs and pins to the module are fine, the module itself is fine, the plugs and pins to the ECM are fine. I tried unplugging an abs sensor and the light on the dash doesn't come on. The front leaf springs were changed recently so I'm guessing whoever did that missed plugging something in on the main harness. If anyone has any insight on this I would appreciate it. |
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aaronwilmoth80911
Top Member
538 Posts |
Posted - 09/16/2015 : 11:37:40 AM
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| It is most likely a J1939 problem. Any time I have experienced any type of "COMM FAIL" on a BB, it is a J1939 problem. Do you have any diagnostic information for J1939? |
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eshover
Senior Member
146 Posts |
Posted - 09/16/2015 : 12:24:09 PM
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Do you have a Bendix 8U1869 remote diagnostic tool? This should tell you where to go look for a problem.
ED |
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bullshark102
New Member
5 Posts |
Posted - 09/16/2015 : 12:39:40 PM
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| No unfortunately our shop doesn't have a bendix diagnostic tool so I'm having to solve this the "old fashioned way". I was able to find a schematic on the abs system and discovered that there is an interface in between the module and the frame harness but I'm stumped as to where it's located. I'm not too familiar with J1939 issues though perhaps you could enlighten me. Which module does J1939 refer too? |
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eshover
Senior Member
146 Posts |
Posted - 09/16/2015 : 2:26:31 PM
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I am not that familiar with the J1939 but I know the tool will guide you to a problem sometimes. All it does is plug into the diagnostic plug in down and to the left of the steering wheel. It cost $75 several years ago.
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Thomasbus24
Administrator
USA
4547 Posts |
Posted - 09/16/2015 : 2:40:30 PM
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| J1939 isn't a module but the electronic backbone of the bus. It's the data line that links engine, transmission, brakes, etc. A twisted pair of green and yellow wire are the backbone. |
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bullshark102
New Member
5 Posts |
Posted - 09/17/2015 : 07:46:15 AM
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| Where is the location of these wires? Would it most likely be a short in that region of the harness? As far as purchasing the scan tool, there are extenuating circumstances as to why I can't or shouldn't purchase it. |
Edited by - bullshark102 on 09/17/2015 07:49:19 AM |
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Thomasbus24
Administrator
USA
4547 Posts |
Posted - 09/17/2015 : 09:14:47 AM
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I don't know how to say this and not sound like a total di**, but if you don't even know what J1939 is, you aren't the guy to attempt to repair it. There's no shame in that though.
That said, if you decide to proceed, I would think the problem would have to be ths node (between the) ABS controller and the main chassis harness up in the frame rail.
Seems like if there was a break in the main main line, your be having so many other issues that the bus would be all but inoperable. Anybody else want to chime in? Could this be as simple as a programming issue in the master gauge?
You can unplug, check for green fuzzy, clean seal and reconnect plugs. Other than that it sounds like you are in over your head.
Issues I've personally had are rub through in areas where clamps hold the main harness up and termination resistor failures. Each time the first symptom has been loss of speedometer and transmission not going into lockup. Dirt gets in the wire loom and rubs the wire insulation to oblivion. |
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aaronwilmoth80911
Top Member
538 Posts |
Posted - 09/17/2015 : 09:26:29 AM
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The J1939 on Blue Birds with C7s (Visions at least) is prone to failure. From what I've seen and heard, it tends to get pinched somewhere behind the engine and has a failure. Are any of your gauges wagging from side to side constantly? Is your ABS light on? It is possible that perhaps the ABS module got screwed up somehow, but from experience I've seen more J1939 issues as opposed to an ABS module just going out. I have a diagnostic form for J1939 harnesses, if you give me an email address, I can email it to you. Or, you can call your Blue Bird dealer and request this info from them.
Just an FYI, a new J1939 harness costs around $700. |
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RonF
Top Member
867 Posts |
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bullshark102
New Member
5 Posts |
Posted - 09/17/2015 : 11:42:43 AM
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| I can understand getting someone certified to do this job but being in the military plus stationed overseas we don't really have the luxury of dealers in relatively close proximity, not to mention time zone differences compared to the states. Although during the winter time the roads are salted here so I would probably guess that the corrosion is caused by that. |
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RonF
Top Member
867 Posts |
Posted - 09/17/2015 : 12:07:58 PM
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Bullshark,
WHere are you located? If you can find the wiring that has those type of connectors in the picture I posted, start there. Go to your ABS controller and peel back the wire loom and look for the green and yellow wires that are twisted together. Disconnect the connectors and look for pushed back pins. Coat the connectors with Dielectric grease when you put it back together. |
US Army retired CMBT |
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Thomasbus24
Administrator
USA
4547 Posts |
Posted - 09/17/2015 : 4:25:46 PM
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quote:
Originally posted by bullshark102
I can understand getting someone certified to do this job but being in the military plus stationed overseas we don't really have the luxury of dealers...
I wish you had said that before. You can understand why we get twitchy when someone starts asking questions about major bus components and has an obvious lack of knowledge and it. A hack working on a school bus in a backyard garage can have tragic results. That isn't the case here though (the part about the backyard hack).
Check the things we've mentioned and let us know what you can find...we'll figure this out! Also, thank you for your service. Great to have you here! |
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bullshark102
New Member
5 Posts |
Posted - 09/18/2015 : 07:03:03 AM
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| I am in Germany currently and thank you I will give that a try. Appreciate the quick responses. |
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RonF
Top Member
867 Posts |
Posted - 09/21/2015 : 08:33:12 AM
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| Retired Army here, spent 8 years in Germany, 85-93. |
US Army retired CMBT |
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Abs Comm Fail
