Non-standard PIDs
The majority of all OBD-II PIDs in use are non-standard. For most modern vehicles, there are many more functions supported on the OBD-II interface than are covered by the standard PIDs, and there is relatively minor overlap between vehicle manufacturers for these non-standard PIDs.
AutoEnginuity, who manufactures OBD-II scan tools, provides the following example on their website:
Although Ford does implement the largest subset of the OBDII standard, the typical vehicle only supports 20 - 40 sensors and is limited to the emissions powertrain. Using the enhanced Ford interface, a typical Ford vehicle will support 200 - 300 sensors within half a dozen systems; that's essential systems such as ABS, airbags, GEM, ICM, etc.
Our enhanced Ford interface coverage is only matched by factory tools; we have support for 3,400+ sensors selected from all 58 systems.
There is very limited information available in the public domain for non-standard PIDs. The primary source of information on non-standard PIDs across different manufacturers is maintained by the US-based Equipment and Tool Institute and only available to members. The price of ETI membership for access to scan codes starts from US $7500
However, even ETI membership will not provide full documentation for non-standard PIDs. ETI state
Some OEMs refuse to use ETI as a one-stop source of scan tool information. They prefer to do business with each tool company separately. These companies also require that you enter into a contract with them. The charges vary but here is a snapshot of today's per year charges as we know them:
GM $50,000
Honda $5,000
Suzuki $1,000
BMW $7,000 plus $1,000 per update. Updates occur every quarter. (This is more now, but do not have exact number)
Read more about this topic: OBD-II PIDs