Check trans light

[Offloader]

OK guys I need some help. I have been all over multiple forums and cannot find the information I need. I have a 2005 holiday Rambler Neptune with an ISB 300 cummins and a 2500 MH Allison transmission. I have the arnes controls. Therefore cannot get codes out of the control panel That is not available on a 2500. On the controls about 15 seconds after I start the coach the check trans light comes on and as soon as I put it it into drive the controls come up as DD. About 15 seconds after that or 30 seconds after a start the coach the check engine light comes on. It appears to be J 1939 isn't working.. I cannot find the location of the transmission control unit and I cannot find the connectors for Jay 1939 any help diagnostics would be wonderful thank you.

[allison_tech]

They put the trans controller or TCM in a variety of places in RV's. Most of the time I have found them under the bed in the master bedroom. If you lift the bed there should be another access door that will expose the top of the transmission. Typically it is mounted to the body somewhere under there. However that is just one place I have seen them. Could be in any of the storage compartments, in the front end behind the grill. Good luck

[Offloader]

Found it thanks

[Ajenness]

Hi, I too have a 2005 Neptune with a check transmission and stop engine lights on. Where did you find the TCU? It’ has the code U0100 “lost communication with ECM/PCM.”

I’m planning on checking and cleaning all connections. Any thoughts?

Thank you!

[153stars]

I have very large module in lower left side dash I assume is TCM . 95 Monaco
I think some newer ones had fuses in them under the cover.

[allison_tech]

That is most likely not the TCM, most tcms do not have fuses directly mounted to them. That could be house or chassis module

[153stars]

I guess I meant VIM not ECM surprised didn't understand what I meant.