J1939 9 Pin to OBD 2 Female Adapter Cable,Work with Truck Diagnostic Scanner Type 2 Green J1939 Diagnostic Connector,OBD to 9 Pin J1939 Y Cable Fit for Heavy Duty Commercial Truck ELD GPS

This is a lesson in reading ahead before making a decision. I got as far as "OBD2" and thought this would be great for adding to my diesel pusher motorhome. Then I could carry one OBD2 diagnostic tool for both the motorhome and the Jeep I'm towing behind it. So I plugged it in, plugged in my OBDLink MX, and looked at the data. Some things worked. Most didn't. Then there's that "reading ahead" part. J1939 is a CANBus protocol just like OBD2. However, car OBD2 data protocol is PID, or Parameter Identification. One parameter, one piece of data. J1939 protocol is PGN, Parameter Group Number. As the name implies, it has a group of data associated with it. Then there is the SPN, or Suspect Parameters Number. This is a basically superset of PIDs. So I was able to decode a couple of SPNs, but no PGNs. Oops.So it works, as long you understand what "works" means. If you have a OBD2 reader that supports ELM327, you should be able to get raw data and decode it separately. My cheapo OBD2 reader actually worked better in that regard than the fancy OBDLink. However, I happen to own a dedicated J1939 reader that works just fine so I'm not pursuing this any further. The bottom line - works as advertised!