National Instruments CAN 372139B-01 - Manual (Page 272)

Chapter 6 Automotive Diagnostic Command Set API for C
Automotive Diagnostic Command Set User Manual 6-108 ni.com
Description
The usual procedure for getting a security access to the ECU is as follows:
1. Request a seed from the ECU using ndUDSRequestSeed with access mode = n.
2. From the seed, compute a key for the ECU on the host.
3. Send the key to the ECU using ndUDSSendKey with access mode = n + 1.
4. The security access is granted if the ECU validates the key sent. Otherwise, an error is
returned.