What communications protocol does DDEC III use?

belfert · May 01, 2009, 09:31:12 AM

Does the DDEC III use any sort of standard data protocol like J1939?

Don Fairchild · May 01, 2009, 10:23:27 AM

Brian;

you are correct on the protocol.

The DDEC II uses a J 1708 the III-IV uses a J1939

Hope this helps

Don

belfert · May 01, 2009, 10:26:57 AM

Is the diagnostics port for the DDEC III standard J1939 then? Could an electronic dash that is J1939 be plugged into that port? I notice the port is simpkly four pins.

Don Fairchild · May 01, 2009, 10:46:51 AM

I don't know if you can plug the electronic dash in, I would think you could. The diagnostic connector and communications harness I show are both 6 pin a-f

You should be able to pull harness off of the com connector for your dash

Don

belfert · May 01, 2009, 12:14:33 PM

The connector itself I believe is 6 pin, but only four of the pins appear to be populated on mine. I'll have to look again.

I'll do some more digging and see what I can find in my wiring diagrams and Series 60 service manual.

belfert · May 01, 2009, 03:14:19 PM

I read Jim Shephard's web site about his Series 60 installation and he had problems with J1939 on the DDEC III. It wasn't enabled and Detroit couldn't enable it. He had to go to DDEC IV.

Maybe the use of J1939 is going to be a moot point for me.

Don Fairchild · May 01, 2009, 04:51:47 PM

Brian;

I went back and looked at the com pic and it shows 5 pins used. The III?IV and the IV use the same protocol.

I do know about jim's issues but don't know why he had them. Remember he repowered his yours came this way. You may not have the same issues.

Don

rv_safetyman · May 02, 2009, 05:05:54 AM

Brian, I will give you a quick answer since I have to run to our trade show this moring.

I THINK that all DDEC uses J1708. It is the transmission that uses other protocols. In my case, my transmission needed the J1939.

I will refer you to a SilverLeaf document that might help a bit: http://www.silverleafelectronics.com/files/J1708-J1939%20Diagnostic%20Connectors_0.pdf

Data ports use only two wires per protocol plus the power wires. So, the J1708 uses two data wires and the two power wires. If you add J1939, you add two more wires. You will see that in the SilverLeaf document.

If you are thinking about buying an electronic dash out of a motorhome, I think it will work. Ron The Busnut sells these units and could tell you.

Two more thoughts. From the above, it should be obvious that the DDEC IV can communicate with both J1708 and J1939. The SilverLeaf products communicate with both protocols. There are some different communication identification codes (part of the protocol). For example, the air inlet temperature identification code is different for DDEC than for Cat and Cummins. I think there are only a couple of those differences, so it should not impact a dash swap to any great degree.

I will check in later tonight and see if this helped.

Jim

belfert · May 02, 2009, 06:51:22 AM

I've thought this through a bit more and I am wondering if I really want an electronic dash. I would basically be depending on the sensors that feed the DDEC instead of sensors that are independent of the DDEC. I would also lose my GPS speedometer.

I'm thinking regular gauges at the dash plus Silverleaf PC might be better. The electronic dash from Ron the Bus Nut is more expensive than Sliverleaf software. I wonder if I could find a 7" or so LCD monitor to mount in the dash above the really important gauges?

Anyone have a schematic for the pinouts on a DDEC III? I looked in my Series 60 service manual, but it doesn't appear to be listed there. I looked at the wiring diagrams for my bus and the function of the pins is not listed. There are a bunch of wires from the DDEC shown on the DDEC/ATEC wiriing diagram with wire numbers, but appearing to go nowhere. I can't tell if they are unused, or if they go somewhere, but no explanation where they go.

belfert · May 02, 2009, 07:11:45 AM

Quote from: Don Fairchild on May 01, 2009, 04:51:47 PM
I went back and looked at the com pic and it shows 5 pins used. The III?IV and the IV use the same protocol.

I do know about jim's issues but don't know why he had them. Remember he repowered his yours came this way. You may not have the same issues.

Interesting. My diagnostics port only has four pins used and four wires going to it. That seems to jive with the Series 60 service manual and the Silverleaf PDF Jim posted. The diag port only does J1708 from what I can tell. J1939 would need to be run from the DDEC most likely.

I'm not sure why a repower versus installed new would matter. Presumably Jim took the original DDEC III to a Detroit dealer and they tried to activate J1939. The local Detroit shop says they would charge one hour to check and activate J1939 on mine.

rv_safetyman · May 02, 2009, 01:53:04 PM

Hi Brain. I am getting a bit confused here. Unless the dash you are looking at **HAS** to have J1939, there is no reason to try to use J1939. My guess is that most electronic dashes have no problem reading J1708 data.

Having said that, if your transmission is a World version, you may have the J1939 activated already. But, again, you don't need it for dash type data.

As you know, I sell the SilverLeaf produicts. Without question, you should consider that option. That gives you the actual engine sensor information. The engine sensors are very reliable (they are part of the emission control system and their accuracy and reliability are mandated by emission control "laws"). That gives you two different pictures of your engine (engine sensors and auxiliary gauges). At: http://www.rvsafetysystems.com/Silverleaf3.htm, I show a couple of screen captures of my VMSpc. I could go on for paragraphs about how great the system is, but the two powerful features I use are the odometers (have 4, one of which is a very accurate fuel gauge) and the fact that it captures and archives fault codes. I also have to drive by the inlet air temperature, since my charge air cooling system are a bit marginal.

All SilverLeaf products talk to J1708.

I talked to the Cummins folks at the show and all current Cummins use J1939. However, from about 2002 back they used J1708. I know that the SilverLeaf can talk to both old and new Cummins, so it must be able to get data from either protocol.

All data ports for truck/bus electronic engines use the same wiring (repeat all). Some are nine pin and some are six pin. Those wiring configurations are shown in the SilverLeaf document cited earlier.

One last thing. For sure the DDECIII is J1708 based. It is supposed to have the capability to activate the J1939 in order to communicate with other equipment. Mine could not be activated for whatever reason.

Jim

belfert · May 02, 2009, 02:09:08 PM

As far as I can tell, the electronic dash requires J1939. I do have a World series transmission so perhaps J1939 is already enabled. I guess I would have to go to the Detroit Diesel dealer to know for sure, or just try something that needs J1939.

If the DDEC sensors are really good then either the Silverleaf or the electronic dash should work fine, but I think the Silverleaf would be a better product.

rv_safetyman · May 02, 2009, 03:40:36 PM

I did not reread all of this thread, so I not sure if a mapping program is in you future. If it is, then the SilverLeaf VMSpc is a great option, as you can have engine data and mapping on one screen

Speaking of engine data, you can get a lot more information from SilverLeaf. For example, I mentioned air intake temperature. That is an important piece of information, but you won't find a gauge for it. Same for MPG, fuel rate, cruise control mph setting, etc. Of course, I am a confessed data junkie

One consideration is where the PC is mounted. On various forums folks have suggested that an operating computer (or TV) on the dash can land you in a bunch of trouble with the law. I mount my computer behind me and have it drive a monitor over my head. That way I don't have to deal with sun shinning on computer screen.

Jim

belfert · May 02, 2009, 04:59:42 PM

I have no immenient plans for mapping software although there are GPS receivers and mapping software very inexpensive for PCs. The bus doesn't get used enough for GPS to make sense. The one yearly trip I could practically drive in my sleep. Once on the interstate there are two or three right turns and two or three left turns the entire 2000 mile trip.

Would a computer screen in the dash displaying the same data as the gauges really cause an issue? (If keyboard/mouse are hidden) What are the legalities of the Silverleaf glass dash? (No chance of buying a glass dash for me.)

Would a small computer monitor 10" or less really have enough size and resolution for the VMSpc display?

rv_safetyman · May 02, 2009, 06:27:06 PM

Brian, I am not a legal expert. Here is my take on it. I believe the intention of the law is to make sure that folks are not playing with a computer or watching TV so that they are distracted. Some states are banning the use of cell phones for the same reason.

However, a monitor is not a device that needs input. It is relaying information just as any gauge would do. Thus, I would think that any judge or jury would agree that it is a "passive" device giving needed information.

You bring up the SilverLeaf glass dash. That is an option in some coaches and is the ONLY dash. Obviously it is legal.

My understanding is that GPS displays are considered acceptable by most (all?) states. That is mind boggling to me! I have been in cars where the driver played with the locations option and totally lost focus on driving. I do not consider GPS to be "passive" units if the driver plays with them.

For my application, I have a wireless mouse that will let me do minor things to the computer. I am careful to tell my wife when I need to do something and she is my second set of eyes. If I get stopped, the mouse will be long gone.

Jim