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Waterloo · 06-13-2016, **(Subject: ABS issue 2008 ProStar )**

Bill, you got me, but all the problems went away when we swapped it out as did the codes. I believe it has had issues from the day I bought the truck. The ABS trailer light would sometimes come on, then it started as a regular thing, then the tractor ABS started, then we got to the situation I have now. Near as I can figure, this compass module has been dying a slow death. And here is the kicker, it is tied directly in to the datalink that also controls the ABS module. I should have the new module this week, I will know for sure once I install it.

The ABS system checked out fine... The compass module was blowing the codes.

I found this, page 23, cab J1939 compass and ABS effects... The ABS and compass modules are connected according to these schematics.

http://bodybuilder.navistar.com/General/...s08339.pdf

Billdozer2 · 06-13-2016, **(Subject: ABS issue 2008 ProStar )**

(06-13-2016 )Waterloo Wrote: Bill, you got me, but all the problems went away when we swapped it out as did the codes. I believe it has had issues from the day I bought the truck. The ABS trailer light would sometimes come on, then it started as a regular thing, then the tractor ABS started, then we got to the situation I have now. Near as I can figure, this compass module has been dying a slow death. And here is the kicker, it is tied directly in to the datalink that also controls the ABS module. I should have the new module this week, I will know for sure once I install it.

The ABS system checked out fine... The compass module was blowing the codes.

I found this, page 23, cab J1939 compass and ABS effects... The ABS and compass modules are connected according to these schematics.

http://bodybuilder.navistar.com/General/...s08339.pdf

Looking at the diagram, it looks like the ABS module is where the terminating resistor is for the CAN bus, which is the same as a car. With the compass module being on the same CAN bus, if the module were to fail, it could cause ABS fault codes for communication issues, which makes sense as you told us that is what the dealer was saying.

(06-13-2016 )Waterloo Wrote: Took the truck to the dealer, checked wheels, all is tight. But, we kept getting a datalink non communication code.

I'm just confused why it took this long to set a fault. You may be on to something where the compass module was communicating fine over the CAN bus, but it may have been an invalid signal for the instrument cluster, and that is why it did not display properly.

I could be incorrect though. It's been years since I've dealt with datalinks, CAN busses, and what nots. Electronics make my brain hurt.

Waterloo · 06-13-2016, **(Subject: ABS issue 2008 ProStar )**

Makes my head numb too... Mechanic said he is 90% sure this is the problem according to what the software said. The Bendix software showed all was fine, as did a visual inspection. Now, the Diamong Logic went directly to the compass module. We both kind of worked together on this. Two heads are better than one, and I hope this solves the problem.

snailexpress · 06-13-2016, **(Subject: ABS issue 2008 ProStar )**

(06-13-2016 )Waterloo Wrote: Makes my head numb too... Mechanic said he is 90% sure this is the problem according to what the software said. The Bendix software showed all was fine, as did a visual inspection. Now, the Diamong Logic went directly to the compass module. We both kind of worked together on this. Two heads are better than one, and I hope this solves the problem.

Here is some good J1939 info for dummy. Page 65 -66 highlighted with yellow will explain you why the compass affect the ABS.