If an '05 Corvette (LS2) is supposedly OBD II compliant, SAE J1850 serial data class 2, shouldn't any OBD II scanner, including EFILive, be able to communicate with the vehicle modules such as the ECM?

The reason I am asking is that I have attempted to communicate (scan) 2 different '05 C6's with three different scanners, including EFILive, and have been unsuccessful. After checking around, others seem to be having the same problem (Vehicle not detected).

My real query is the understanding of the OBD II standard(s). Isn't it supposed to legislate, mandate, a standard interface and protocol so that multiple equipment and service providers can provide/access the vehicle service information? Has the standard changed, is GM still compliant if a generic OBD II scanner cannot communicate with the vehicle?

Thanks.

Bob