User´s Manual - I+ME ACTIA GmbH

Security Access - request seed
The purpose of the service ($27) Security Access is to provide a way to access data and/or diagnostic
services, which have restricted access for security, emissions, or safety reasons.
The security concept uses a seed and key relationship. The seed and key are each 16-bit numbers (2
byte). The key has to be sent to an ECU to enable ("unlock") Cat's access to specific services. The seed
using an encryption algorithm can derive the key. Therefore an individual seed is stored on each ECU.
CAT provides two already predefined setup levels of the Security Access service:
- The Security Access – request seed (sub-function parameter = $01 or $03),
- The Security Access – send key (sub-function parameter = $02 or $04).
To setup the sub-function parameter to request seed $01 or $03, the Setup button in the Main Diagnostic
Setup window could activate the dialog box shown below.
Sub-function parameter $01 is the request seed level used for ECU programming via the SPS system.
Sub-function parameter $03 is the request seed level for enabling vehicle manufacturing specific device
control restrictions (as opposed to having service device control restrictions enabled).
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