Calling all DDEC2 experts

[rgwilliams]

I have a 4104 that was repowered by the previous owner with a 6V92 DDEC2 and VR731 ATEC.   I recently purchased a VMSpc (by SilverLeaf Electronics) to monitor fuel economy, among other things.  The odometer value sent from from the DDEC will only work sporadically.  This sounds similar to Sean's problem 2 years ago, but is slightly different.  The speedo on the VMS works, as does the cruise set speed , as do the instantaneous and recent fuel MPGs. (How that can be with no odometer I don't know). 
I drove to the DD service center this pm and he hitched his Prolink up and it shows the same odo reading as the VMSpc , so I know it's not the VMS unit.  When he checked to see the pulses per mile, at first it read "not set", and then while I was looking for data to input, it showed a value set, with no input from the Prolink.  We reset the  pulses per mile and I went for a drive and same results.  Speed perfect, and the odo only increases when it feels like it, and bears no relation to distance travelled. Is this a wiring or ECU problem? Any ideas?
Thanks
Rob W

[luvrbus]

RG, have you downloaded all the upgrades from Sliverleaf, all of the VMS units I have been around don't like the DDEC 11 for what ever reason.Jim Sheperd is the local Sliverleaf guy on this board.Have you called Sliverleaf they have techs to help and on line help also.Which diagnostic pin do you have the 6 or the 9 I know a little about the VMS and they can be a pain trying to get everything to work with a DDEC11  good luck

[rgwilliams]

luvrbus

That's what Silverleaf told me (poor com with DDEC2), but in this case the DD dealer's scanner is getting the same number as the VMSpc.  I have no documentation for the DDEC ATEC conection and the previous owner had some "loose ends" that might have been important.

Rob

[rv_safetyman]

There are several VMSpc units out there on DDECII.  I don't think that the software version is a huge deal.  Having said that, it is always good to download the latest "stable" version.  That is currently 2.4 build 2.  Starting with the 2.4 versions, you can now view your Pressure Pro tire pressure sensors on the VMSpc screen.  You can see all the tires at one time (all the time) in both pressure and icon view (or both).  That requires a bridge to receive the PP sensor signal and convert it to the data stream that the VMSpc expects to see.

Sorry got off subject.  Since the ProLink got the same problem, I suspect that there might be a wiring issue in the cable from the ECM to the front data port. 

If you want to play with it, take the VMSpc and computer to the back dataport and see if you have the same problem.  As I recall, the DDECII does not have the conventional data port.  You may have to adapt.  If it works OK in the rear, you probably have a problem with the twisted pair of wire running to the front.  If that is the case, you will need to run a new twisted pair.  Before I did that, I would check the connections on both ends.  Take apart the connectors and spray them with something like CorrosionX and put them back together.

I don't think the ECM has a problem, or you would have performance issues.

Jim

[rgwilliams]

Jim

Thanks for your reply.  I am running 2.4 build 2.

On the VMSpc forum there was, buried in the 2.3beta thread, a query, from someone who had exactly the same symptoms I have.  His handle was "rvinternet".  I'm trying to get a reply from that forum to see what  his solution was, or if he had any resolution.

I didn't see the prolink screen as the tech manipulated it.  He only asked about a speedo drive or sensor.  I wonder if there was a 3rd choice of ATEC input on the next line down.  Do you know if that's the case?

Rob

[Sean]

This is not a VMS issue, it's the DDEC.

I have the same problem -- my speed reads good, but my "odometer" has been stuck on the same value since I got the coach.

Instantaneous and "rolling" MPG are calculated by the Silverleaf differently -- they do not rely on the odometer reading.

I have never been able to get an answer out of Detroit on this.  Let me know if you do.  But this is definitely NOT Silverleaf's problem.

-Sean
http://ourodyssey.blogspot.com

[luvrbus]

You have problems with the Pro-Driver installed on a DDEC11 they work great on the DDEC 111 but not the 11     good luck

[rgwilliams]

Sean
Agreed, I didn't think it was a Silverleaf problem at all.  I'm beginning to suspect the conversation between the DDEC and ATEC computers from where both the prolink and vms get their info.  I've located others with the same problem, all DDEC2s, and they have never solved it.  The fuel economy reading from the "recent" gauge will have to do, I guess.

Luvrbus
Never did try a Pro-driver, but I did lust over the ones in the wreckers' parts bins. I had the advertising literature and they looked pretty cool. They still wanted $400 with no harness or connectors or documentation.  But now, it looks like it wouldn't have worked for mileage either .

[Sean]

...  I'm beginning to suspect the conversation between the DDEC and ATEC computers from where both the prolink and vms get their info.
...

There are very few connections between the DDEC and ATEC.  I originally had a problem with this connection, which is why I did not even get a "speed" reading.  The interface is strictly for TPS information to the ATEC, and speed information to the DDEC.  In my case I have the "Maximum Feature Throttle Interface,"  and I had a bad wire, which I fixed.  Now that the speed info is getting to the DDEC correctly, there is nothing further to do with the interface.  DDEC-II can not "talk" or "listen" to the ATEC electronically the way more modern CAN-based systems do.

  I've located others with the same problem, all DDEC2s, and they have never solved it.  The fuel economy reading from the "recent" gauge will have to do, I guess.

Whenever I talk to Detroit, they say it "should" work.  But when I say "fix it" all they can do is shrug and tell me that for $2,000, they can re-program the ECM to "see" if it will work.  I have offered several times to pay the $2,000, but only after they can prove the problem is fixed.  They won't do it, so we have a stalemate.  I don't know anyone else (except you, now) with a DDEC-II that has a monitor on it (VMS, Pro-Driver, or even Pro-Link) to check.

Never did try a Pro-driver, but I did lust over the ones in the wreckers' parts bins. I had the advertising literature and they looked pretty cool. They still wanted $400 with no harness or connectors or documentation.  But now, it looks like it wouldn't have worked for mileage either .

There is absolutely no benefit for a Pro-Driver over a VMS.  They both connect to the same data stream and display the same information.  Neither can tell you anything that the DDEC ECM does not, itself, know.  As we used to say in the computer biz, GIGO (garbage in = garbage out).

Without a correctly increasing odometer reading, "average" fuel mileage can not be computed, because the VMS simply takes the total fuel used since last reset or trip reset (by keeping a running total based on the GPH figure from the DDEC and the internal clock) and divides by the difference between current odometer and odometer at master or trip reset.  Several other features of the VMS system are also rendered useless by the lack of odometer information, including the maintenance interval reminder and log, and the trip meters.

By contrast, instantaneous MPG does not use the odometer -- it is quite simply the current speed, in MPH, divided by the current fuel flow rate, in GPH (miles/hour divided by gallons/hour equals miles/gallon -- no "distance" is needed).

The other MPG figure, which on my VMS-200 is called "rolling MPG" and on your VMS-PC is apparently called "recent MPG" is a completely fabricated number, useful for almost nothing, and I don't know what Silverleaf was thinking when they created it.  As near as I can tell, it is a time-average of the instantaneous MPG I just described, over the last few minutes (I think five).  Since the VMS knows instantaneous MPG, by the method I just described, and since this number is a time average of that figure, rather than a distance-based average, again no odometer reading is needed.

Again, changing to a Pro-Driver or any other monitor will not help, because the missing information is the odometer reading from the DDEC.  No amount of sophistication in the reader device can make up for information missing from the DDEC (and, IMO, the VMS is actually a much more sophisticated monitor than the Pro-Driver anyway).

This is maddening to me, because I can't understand why the DDEC is not incrementing the odometer when it is clearly seeing speed pulses from the speed input.  Miles are just speed over time, so all the underlying information is there to do it.  Also, my DDEC clearly has numbers in it for the odometer and the "time at idle," but they never change.  I have no idea where those numbers came from in the first place.

If anyone here has in depth knowledge of the inner workings of the DDEC ECM and knows how to fix this (even if that means paying for some specific program change), I'd love to hear from you.

-Sean
http://ourodyssey.blogspot.com

[blue_goose]

I installed a silverleaf in a friends Wonderlodge with a dd2 and it worked fine.  It is a 1990 don't know what they did, but it worked.  Where are you trying to get the info from?  Do you have a plus sender or are you trying to get it from the odometer?
Jack

[Sean]

Jack,

The Silverleaf gets all its information from the DDEC ECM.  It is a very simple two-wire interface, there is nothing else to connect.

The DDEC gets speed information from any one of a choice of senders.  On most ATEC-equipped coaches, the tailshaft revolutions are sent to the DDEC by the ATEC through a very simple pulse interface.  This is the case on my bus.  This interface is working;  my DDEC correctly reports vehicle speed after properly programming the differential ratio (in my case, 4.3:1) and the tire revs/mile (in my case 480).

The DDEC keeps an internal Odometer, and also an engine hour meter.  On my DDEC, and apparently others, the Odometer function inside the DDEC ECM is not working.

-Sean
http://ourodyssey.blogspot.com

[blue_goose]

Sean,
Just a statement, that the one on the Wonderlodge did work.  I also have a silverleaf and my son has one also.  They are both on DD4.  The one that I put on my friends Wonderlodge gives you the same info that the others I have installed.
I will also check his with my prolink the next time I am in NC.  I will make a better post after that happens.
Jack

[Blacksheep]

Prevost offers and has a listing actual part numbers for the Pro Driver for my 1992 8v92 DDEC 2. If they were or are missing info in order to work properly, why would they have them listed and equipped on some units already on the road. My friend has one in his and it works flawlessly!
Could it be that the ecm that is in question has a problem internally? I know they are built tough but things can happen over years of use!

Ace

[Sean]

Ace,

Yes, I suspect there is a "problem" with the ECM.  However, the problem did not go away after changing ECM's.  Since they simply load your entire configuration into the other ECM when they swap them, I suspect my problem is in the configuration.

Again, I asked Detroit if they can pull the config from the mother shop and reload it.  That's what they quoted me $2,000 to do, with no refund if it does not actually fix the problem.

I've talked to dozens of DD technicians about this, and not a single one can tell me why these numbers do not increment properly.  I thought I was all alone in this regard, but this thread has informed my that at least a few others have the exact same issue.  If someone here knows exactly what to set or change in the ECM, or what program change would be needed from Detroit, I am all ears.

-Sean
http://ourodyssey.blogspot.com

[JohnEd]

Sean,

Back in the day, as a last resort OR to prove a theory, swapping the suspect module was done....and taught by me.  My rule was that it wasn't enuf to "cure" the problem...you have to prove that the problem "follows" the module.

There seems to be Silver Leaf systems out there that work on DD II.  Is there an owner out there that would swap your ECM into his system and verify the operability of his system?  Next step would be to install their ECM in your system to "prove" the conclusion if yours doesn't work in theirs.  Both of you are mobile....?  With your rep and credential I think I would hold out hope that a deal could be struck.  Jack seems to have a handle on one and with his involvement....?  That still wouldn't split the hair of software or hardware, but?

As I read this I thought back to the most "maddening" problems I had ever encountered.  Almost every one involved multiple failures that trashed all logic.  I guess that won't be proved till you find the "one".

Good luck on this.  That you are stumped scares me a little cause I have a small idea of your capability.

John