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

After sending the ReturnToNormalMode ($20) request, the Tester must wait 1 s to allow 
sufficient time for all nodes to reset and synchronize. 

The tester suspends transmission of Tester Present ($3E) messages at this time.
 
 
Note:
Following a ReturnToNormalMode ($20) service the determination of the diagnostic addresses and 
diagnostic CAN Identifiers (using the service $1A with DataIdentifier $B0) is performed automatically prior to 
the execution of a diagnostic service. See Table 232, Step 29. 
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GM WORLDWIDE ENGINEERING STANDARDS 
GMW3110 
© Copyright 2010 General Motors All Rights Reserved 
February 2010 
Page 279 of 336 
Following the ReturnToNormalMode ($20) service additional action can be performed for each ECU (utility file 
driven - interpreter execute) to finalize the programming. This part contains all steps required to finally 
conclude a programming event of a single ECU. For some nodes it may be required to write data after the 
software reset, when the operational software is running. Those steps are contained in the ECU specific utility 
file. See Table 232. 
This part is utility file driven except for the determination of the GMLAN communication parameters (CAN 
Identifiers). 
Table 232: Optional Utility File Steps Following the Programming Conclusion Step 
Step 
Action 
27 
Wake-up link(s) - 
High voltage wake-up for SWCAN
- gateways may cascade wake-ups (where 
applicable) across to the other subnets on the vehicle or the tester may need to use 
level $04
of 
diagnostic service 
InitiateDiagnosticOperation ($10)
to generate the wake-up (functionally 
addressed to gateway ECUs only). This is necessary because the gateway ECU(s) has (have) been 
reset and might have lost the internal information about keeping a wake-up signal line asserted on 
another subnet on the vehicle.
Note:
The tester must allow at least 500ms after issuing a wake-up before transmitting any diagnostic 
request message (including tester present) to allow the ECU to process the wake-up and transition to 
a communication active state. Refer to paragraph 6.1 for wake-up requirements. 
28 
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