D6

Default ARPC Response Code is the fallback value M/Chip cards use for the Authorization Response Cryptogram verification process when the issuer's actual online response doesn't supply a usable one - related to Issuer Authentication Data (91) and the Authorisation Response Code (8A), both covered earlier, which together are what the card normally relies on to validate that an online response genuinely came from the issuer. A default exists because a card's own logic still needs a defined outcome even in edge cases, a malformed or incomplete online response, for instance, rather than being left in an undefined state - D6 is specifically what M/Chip falls back to in that situation, closing what would otherwise be a gap in the card's own state machine. Because this determines how the card behaves in exactly the scenarios where something has already gone wrong with the online exchange, it's a field worth understanding precisely when investigating an unusual second-GENERATE-AC outcome rather than one that matters during an ordinary, cleanly-completed online transaction. Its source citation carries this cluster's consistent verificar vigencia flag. See Mastercard M/Chip 4 Card Application Specification.