I have a Roadmaster chassis. I looked under the front of the coach, in the engine bay, in the front bins, throughout the shifter console, and through the dash as much as I could without removing components such as the radio, monitor, etc. I don't think I have J connector, or it cannot be revealed without some surgery..
The ScanGaugeD does not come with the connecting cable I need. I spoke with the ScanGauge people, and they have a replacement cable to fit the 12-connector rectangular diagnostics connector under my dash. It is on the way, as is my ScangaugeD.
Thanks all!