APDU response codes.

Use the returned data according to the command.

Use GET RESPONSE as required by the card and transport; SW2 supplies the short response length.

Inspect the command specification; non-volatile memory is unchanged.

Do not assume the returned data is intact.

The response may contain fewer bytes than requested.

Check the file lifecycle and application rules.

Check the selected file and expected FCI format.

Non-volatile memory may have changed; consult the command definition.

X is a counter. For VERIFY, it usually gives remaining PIN/password attempts; other commands may use it differently.

Check the card state and command-specific documentation.

Inspect application state before repeating a state-changing command.

The card reported a storage problem.

Check Lc, Le, and the actual command-data length.

Check class-byte features against the selected application.

Check the channel encoded in CLA.

Check whether this application accepts the requested secure messaging mode.

Check application state and command prerequisites.

Select a file whose structure supports this operation.

Complete the required authentication or secure-channel setup.

Use the documented recovery procedure; repeated guesses will not unblock it.

Check the lifecycle of the referenced object.

Check application selection, lifecycle and preceding commands.

Select the required EF before retrying the operation.

Check the protected command structure.

Check secure-channel state, MAC and encrypted data.

Check the data encoding and required fields.

Check whether the card implements this operation.

Check the AID or file identifier; this does not prove the card is empty.

Check the record number and file selection.

Check space requirements for the operation.

Check each TLV length and the total command-data length.

Check the command parameter bytes.

Check the data length required by these parameters.

Check the requested tag, key or object identifier.

Check P1/P2, including any offset.

Reissue the command with corrected short Le from SW2, if the card profile permits.

Check INS and the currently selected application.

Check CLA, channel and application class.

Consult the application documentation and diagnostic logs.