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Racehlr · 10-09-2019, 05:12 AM

Hello all,

We have a 2008 Tiffin Phaeton 42 QRH 360 cummings on a spartan chassis. The other day when I shut off the MH a few minutes later I heard a alarm coming from the dash area with the following faults showing. "Transmission J1939 Communications fault" / "ABS Fault" / "No J1939 Data Bus communication". I started the MH up and all seem to clear and everything seemed fine. Went back over the next day and alarm was going off again. Not sure where to start or should I just take it to a dealer. MH seems to run fine going down the road with no issues. Just acts up once it is shut off. Thanks for any advice on this.

CountryB · 10-11-2019, 08:05 AM

Get the actual code (use the keypad and count flashes). Need to know what code you have to help with diagnostics.

For example, if code 66-00 then you would follow these steps:

dbarton291 · 10-11-2019, 11:24 AM

What exactly is displaying the faults? Is this an OEM supplied monitoring system or is one of the controllers in the vehicle displaying the fault (i.e. trans TCM, engine ECM)?

That type of situation usually occurs when there is a power down timing issue. The ignition is shut off and the controllers power down at different times. One is left on when the others are shut off and it's expecting J1939 communication traffic and it's not there. Has there been any electrical equipment changed or repaired in the coach recently?

Racehlr · 10-16-2019, 06:32 AM

dbarton291 a few years back the fuse panel on the driver side compartment had some water damage that was taking care of by a dealer. I have had an issue still in there with a fuse now and then being corroded and have had to clean the terminals in the fuse panel. Here is a picture of the display on the dash that shows the error once the MH has been shut off for awhile. Also the ignition unit was loose last year but I was able to tighten in back into the dash and seems to be fine. Someone else said to check all the connectors under the coach. Thanks for any help you can provide on this.

dbarton291 · 10-16-2019, 08:18 AM

You need to separate transmission fault codes from the system that is displaying this message. There is no transmission fault code that has that description. I've looked through all the fourth gen codes for the on highway transmissions and don't see it.
The first step is to determine if the transmission is storing a diagnostic code and what is that code?
If you have a 3/4000 series transmission you can read the codes with the shift selector. If you have a 1/2000 you need a diagnostic reader to retrieve them. Allison uses a program called Allison DOC to read the codes.
If the transmission has a code, fix that issue first.
If the transmission does not show any trouble codes, the issue is somewhere else.
I assume this display you show in the picture is an add on item that is displaying messages from the J1939 datalink. The source of the error message is one of the controllers on that link i.e. transmission, engine, ABS, body controller, etc.
Anyway, determine if there are any transmission diagnostic codes. I may be able to help from there.

Racehlr · 10-16-2019, 08:38 AM

Quote:

Originally Posted by dbarton291

I assume this display you show in the picture is an add on item that is displaying messages from the J1939 datalink. The source of the error message is one of the controllers on that link i.e. transmission, engine, ABS, body controller, etc.
Anyway, determine if there are any transmission diagnostic codes. I may be able to help from there.

dbarton291 no this is the oem dash display which shows miles, mpg, etc. I will have to look up which transmission I have and check that first with a reader. It also displays these other faults too. "ABS Fault" & "No J1939 Data Bus Communication". Thanks for all your input so far on this.

Racehlr · 10-16-2019, 09:06 AM

Here is a better picture of the dash.

Racehlr · 10-21-2019, 07:00 AM

Quote:

Originally Posted by dbarton291

You need to separate transmission fault codes from the system that is displaying this message. There is no transmission fault code that has that description. I've looked through all the fourth gen codes for the on highway transmissions and don't see it.
The first step is to determine if the transmission is storing a diagnostic code and what is that code?
If you have a 3/4000 series transmission you can read the codes with the shift selector. If you have a 1/2000 you need a diagnostic reader to retrieve them. Allison uses a program called Allison DOC to read the codes.
If the transmission has a code, fix that issue first.
If the transmission does not show any trouble codes, the issue is somewhere else.
I assume this display you show in the picture is an add on item that is displaying messages from the J1939 datalink. The source of the error message is one of the controllers on that link i.e. transmission, engine, ABS, body controller, etc.
Anyway, determine if there are any transmission diagnostic codes. I may be able to help from there.

I was able to check to see if I had any codes per your instructions and it came up with D1-- so it must be something else causing the issue. Any idea where to start? Thanks.

dbarton291 · 10-21-2019, 07:10 AM

Quote:

Originally Posted by Racehlr

I was able to check to see if I had any codes per your instructions and it came up with D1-- so it must be something else causing the issue. Any idea where to start? Thanks.

As Clint Eastwood said one time "A man has to know his limitations".
Since this isn't an Allison issue, or doesn't appear to be, there are probably better folks than me to tackle this one.
However, if it were my vehicle, I'd get the documentation for this display that is showing the error and see what it is looking at as well as how it's wired in the vehicle. Then see if perhaps one of the controllers could be powering down out of sync with the others. But again, this isn't my area of expertise.