: The diagnostic tool (like GDS2 or DPS) requests security access from the ECU. Retrieve Value : The ECU responds with a unique 5-byte "seed" value. Calculate Key
The official GM dealership software that handles the Seed/Key exchange automatically via the cloud. gm 5 byte seed key
: For many newer models, the algorithm is no longer stored locally in the diagnostic software. Instead, the Service Programming System (SPS) client must contact GM's servers (such as the IVCS SOAP endpoint) to retrieve the correct key. : The diagnostic tool (like GDS2 or DPS)