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

TesterPresent ($3E)
periodic messages to all nodes - all links as needed (using the 
AllNodes CANId and AllNodes extended address). 
3 
Use service 
ReadDataByIdentifier ($1A)
service to determine diagnostic addresses and CAN 
Identifiers for all ECU(s) (excluding SPS_TYPE_C) on each subnet (setup of base diagnostic 
configuration matrix), 
DID $B0.

This determines the relationship of each ECU
’s diagnostic address and its physical request and 
response CAN Identifiers. 

SPS_TYPE_C ECUs would not respond since diagnostic responses have not been enabled yet. 

This step and the ReportProgrammedState ($A2) service step which occurs later in the process 
allows the utility file to only contain the node diagnostic address. The tester correlates the 
diagnostic address to the physical request and response CAN Identifiers. 
4 
optional 
step 
Send an 
InitiateDiagnosticOperation ($10)
request with a sub-parameter value of 
$02 
(disableAllDTCs)
using the AllNodes request CANId and the AllNodes extended address. 

This step ensures that nodes that poll the CAN controller do not set DTCs if they do not process 
the mode $28 request (in the next step) before they could possibly set signal supervision 
failures. 
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GM WORLDWIDE ENGINEERING STANDARDS 
GMW3110 
© Copyright 2010 General Motors All Rights Reserved 
February 2010 
Page 272 of 336 
Step 
Action 
5 
Send a 
DisableNormalCommunication ($28)
request (with AllNodes CANId and AllNodes 
extended address - on each link as needed). 

This disables sending and processing of normal mode data. 

An SPS_TYPE_C ECU does not respond to the $28 request but tracks receipt of the $28 
request (in order to enable diagnostic responses after receiving the $A2 service later in the 
process). 

The tester shall not enable diagnostic responses in SPS_TYPE_C ECUs (via mode $A2) until 
after it has received positive responses to the $28 request from all other ECUs on the link (as 
stored in the diagnostic configuration matrix). 
6 
Determine which nodes are programmable using the service