All I know is that it's one or the other. Sensis/Whereis is less than forthcoming in stating which version is used by the various car brands. This link is to their Mazda page:
Maybe you could phone or email them as invited on that page:Code:Please Login or Register to see the links
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But I wouldn't bother asking them, you'd probably get better results asking a Mazda dealer.
If anyone else does know, please post to let us know the correct version, not only for Mazda, but also for the Land Rover, Volvo, Ford, Holden, BMW etc models which use the VDO Dayton/Denso system.
Of the others with VDO Dayton/Denso, we already know that all Toyota/Lexus and the earlier Subaru models use C1, and all Mitsubishi and the late models of Subaru use C2. It would also be good to have a clear year date when Subi changed from C1 to C2.