Before STIP begins its checks, it sets all response codes to 00 to default them to an approval. During STIP processing, STIP invokes several functions, for instance, checking expiration dates or the exception files, or processing for services such as Cardholder Authentication Verification Value (CAVV) Verification Service, Card Verification Value (CVV/iCVV) Service, Dynamic Card Verification Value (dCVV) Service, or PIN Verification Service (PVS). Each function generates a result code, depending on the member set-up and on the services the member uses, and STIP holds these individual interim response codes until it finishes processing the message. STIP then selects the response code with the highest priority and inserts it in Field 39—Response Code.

STIP determines the issuer-specified response codes based on the following considerations:

Issuer-specified default response codes.
The default response code override.
The CVV or iCVV failure.
The CVV2 failure.
The CAVV failure.
The dCVV failure.
The PIN failure.
Visa Smart Debit/Smart Credit (VSDC) Service processing conditions.
$150 rule processing conditions.
Suspected fraud

Issuers can specify default response codes for MCGs at the BIN level. Issuers can specify separate response codes for when the issuer is available and when it is unavailable.
If the issuer is available, STIP uses the available response code. Otherwise, STIP uses the issuer-unavailable response code. Issuers can use the following response codes for issuer-available and issuer-unavailable conditions:
00—Approval
01—Refer to issuer
04—Pick up card
05—Do not honor
57—Transaction not permitted to cardholder
83—STIP cannot verify PIN
91—Issuer is unavailable

How STIP works?