General Specification Electrical Function gmw3110 General Motors Local Area Network Enhanced Diagnostic Test Mode Specification

GM WORLDWIDE ENGINEERING STANDARDS 
GMW3110 
© Copyright 2010 General Motors All Rights Reserved 
February 2010 
Page 261 of 336 
Note:
Services $10, $27, and $3B are optional and may not be present based on the type of ECU. 
Note:
The pseudo code flag Service_28_MsgReceived is used by the Boot_Process_Recv_Msg( ) function, 
the Boot _28_Msg_Recvd( ) function, and the Boot_Exit_Diagnostic_Services( ) function to illustrate enabling 
of the special case diagnostic CAN Identifiers used by SPS_TYPE_C ECUs. 
9.3.2.5 Security Requirements. 
All programmable ECUs that have emission, safety, or theft related features 
shall employ a seed and key security feature, accessible via the SecurityAccess ($27) service, to protect the 
programmed ECU from inadvertent erasure and unauthorized programming from the GMLAN interface. All 
field service replacement ECUs that meet the above criteria, shall be shipped to the field with the security 
feature activated (i.e., a programming tool cannot gain access to the ECU without first gaining access through 
the SecurityAccess service). 
All ECUs that support security for SPS shall implement the seed and key relationship supplied by GM Service 
and Parts Operations. Once a security algorithm is assigned, a change to the algorithm shall result in a change 
to the ECU Base Model Part Number. See DID $CC in Appendix C of this specification. 
Note:
A change to the security algorithm shall also result in a change to the utility file needed to program the 
ECU. 
All development ECUs shall use the ones-complement of the seed as the valid key. 
9.3.2.6 The Vulnerability Flag And Manufacturers Enable Counter (MEC). 
The Manufacturers Enable 
Counter (MEC) and Vulnerability Flag are variables which are used to bypass a nodes security system during 
development or during portions of the node and vehicle manufacturing process. The variables 
manufacturers_enable_counter and vulnerability_flag are used in the pseudo code of the applicable diagnostic 
services described within this specification to represent the MEC and Vulnerability Flag respectively. 
Reference the SecurityAccess ($27) service within this specification for more information on accessing node 
security.