04-05-2013, 08:16 AM
Perhaps a little clarification would help. And if any of you have actually wired a VMSpc into your bus, your experience would be appreciated.
We ohmed out the diagnostic port under his ignition key, back to his VMS 230 unit. And according to the VMS connection diagram, the data pins there connected into the J1708 data pins on the VMS.
However, there was no J1708 traffic on those wires when we connected in. Bill then happened to pull up his VMS diagnostic page, which indicated that there were J1939 errors. This is a different protocol, which likely comes in on different wires (the VMS has inputs for both).
Now, I know that Bills coach may be different, in that it's CAT engine, rather than Detroit, but my gut feeling is telling me that the diagnostic connector to under the ignition key is not connected to the engine ECM, but perhaps to the transmission, which may speak the older protocol.
Has anyone got a wiring diagram for the diagnostic connector by the key. Is there perhaps another diagnostic connector location?
The pinouts for that connector are identical to J1708 pinouts of vehicles back in the late 90's. However, his VMS showed J1939 errors, which leads me to believe there is either another diagnostic port, or the VMS is spliced into a different set of wires.
Thanks,
Ray
We ohmed out the diagnostic port under his ignition key, back to his VMS 230 unit. And according to the VMS connection diagram, the data pins there connected into the J1708 data pins on the VMS.
However, there was no J1708 traffic on those wires when we connected in. Bill then happened to pull up his VMS diagnostic page, which indicated that there were J1939 errors. This is a different protocol, which likely comes in on different wires (the VMS has inputs for both).
Now, I know that Bills coach may be different, in that it's CAT engine, rather than Detroit, but my gut feeling is telling me that the diagnostic connector to under the ignition key is not connected to the engine ECM, but perhaps to the transmission, which may speak the older protocol.
Has anyone got a wiring diagram for the diagnostic connector by the key. Is there perhaps another diagnostic connector location?
The pinouts for that connector are identical to J1708 pinouts of vehicles back in the late 90's. However, his VMS showed J1939 errors, which leads me to believe there is either another diagnostic port, or the VMS is spliced into a different set of wires.
Thanks,
Ray