This counts how many passes of the foreground diagnostic test completed successfully. Read together with cardDiagFailures after a multi-pass test run, this tells the admin the pass to fail ratio for that specific diagnostic session, which is the direct evidence used to declare a card healthy or faulty after troubleshooting. For example, after running 20 passes, cardDiagPasses reads 19 and cardDiagFailures reads 1, showing an intermittent fault that only manifested once in twenty tries.