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I have a question for you super sharp technical folks. Is there any reasonable way to check the integrity of a Series 60 engine diagnostic plug short of hooking it up to a Detroit diagnostic computer.

The Pro Driver on my 2003 LXI is inoperable and I am not sure if it is a Pro Driver problem, a wire problem between the unit and the diagnostic plug or a wire problem betwen the diagnostic plug and the engine ECU.

I have not taken the time to remove and diagnose the individual items. Both the Pro Driver and the diagnostic plug are very difficult to access. I have a wiring diagram for both the Pro Driver and the ECU to the diagnostic plug.

Any suggestions or advice would be appreciated.
Hey George,

You'll need an oscilloscope or a a logic analyzer to see what's happening on the 9600 baud J1708 datalink. You can also monitor the J1708 using your computer if you buy something like the busbee: http://www.usbee.com/busbee.html serial bus monitor, but that'll cost about $300.

I assume you're getting power to the ignition switched and un-switched leads and that you have a good ground. If not, here's the document for fuse locations: http://wanderlodgegurus.com/database/ind...0Locations

I scanned the LXi schematics but I can't find where the Pro Driver taps into the datalink bus. The diagnostic port taps in at the Allison ECU which is located in the generator cooling fan bay.

If all the powers and the ground check out, I'd be tempted to jumper around the Pro Driver datalink by running a twisted pair from your diagnostic port to the Pro Driver. I think we can assume your diagnostic port is functioning properly because you had your transmission jake brake preselect programmed recently from 4th to 5th.
On the earlier models, the PD simply plugs into the oem diagnostic and pigtails off a new diagnostic connector.

I think it's done the same way on the LXi. Since George isn't experiencing any issues with his engine, or transmission, or ABS brake operation we can safely assume that his CANbus is working properly. That means if it's a datalink communication issue to the Pro Drive it would have to be an open circuit from the diagnostic port to the Pro Driver. I'd ohm out those connections.
The prodriver apparently wires into the back side of the diagnostic plug. It is difficult to get at and the wiring behind is too short to really be able to pull the plug out far enough to see what is going on behind.

Since I have owned the coach, it has not been plugged into a diagnostic computer to confirm that the wiring to the plug is good. I will have to do this when I get back to America.

I know it has one hot lead to the PD as the light blinks occasionally. The wiring to the PD is very difficult to access. It takes arms 5 feet long with 3 elbows.

I was hoping someone could give me an easy solution that I was too dense to realize on my own.
I've never had issues with my PD, so I'm kinda just throwing things out there. I think from the diag plug the next connection upstream is at the Allison brain (in the genny fan compartment). I'd ohm-out the datalink twisted pair connections from the diag port to the Allison connector. I don't think there are any cannon connections along the way, but I might be wrong. I'll check the schematics as soon as I finish building this carpenter bee trap. Smile

I couldn't get this link: http://wanderlodgegurus.com/database/ind...0Locations
to to work. This was on your first post supposedly for fuse locations.

I have an engine ECU schematic (I believe you sent me) someplace and will see if I can find that but I thought the ECU wiring went direct to the diagnostic plug, not the Allison unit. I may be wrong on this.

I think this schematic shows that the front diagnostic port taps off the datalink at the Allison ECU transmission connector:


Here's the link to the LXi fuse locations that I tried to post earlier:


The datalink starts at the DDEC ECU wiring harness (HC2) and connects to the Frame wiring harness (HC1) at P22/P24. It then connects to the Allison ECU at the Frame wiring harness (HC1) at P24/P4, at which point the diagnostic port taps off.

The following diagram shows the DDEC ECU connecting to frame components (HC1 wiring harness) at connector P22. The DDEC ECM connects at P1.

The following diagram shows the Allison ECU connected to 'frame components (HC1 wiring harness) via connectors P24/P4 and to the engine DDEC (HC1 wiring harness) at P22/P22.

The following diagram shows the datalink connecting from the 'engine interconnect' connector P22 to the Allison ECU at P24 along the Frame Wiring Harness (HC1).

Thanks for all the good info. I am going to have to access the PD and remove it and jumper to the front of the diagnostic plug and then, if necessary, to the ECU to prove the integrity of the wiring.

If all wiring including power is sound, I can assume the Pro Driver has went T.U.
Not specifically for you George but for the rest of our readership. Here's a pdf that explains the symbols used in the schematics:

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