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 100 of 336 
If the setting of diagnostic trouble codes (DTC) has been disabled via the $10, $28, or $AE services, then the 
node shall re-enable the diagnostics and take the necessary steps to reinitialize diagnostic counters, flags, 
timers, etc in order to prevent false DTCs from being set due to the fact that the algorithm was disabled for 
some period of time. 
Note:
It may be necessary for a node to reset certain DTC algorithms or variables used within these algorithms 
prior to executing a software reset at the conclusion of a programming event. 
An ECU shall send an unsolicited service $20 positive response message any time a TesterPresent ($3E) 
timeout (P3
C
) occurs and a programming session is not active. 
Note:
If a P3
C
timeout occurs while the ECU is in the process of receiving or transmitting a multi-frame USDT 
diagnostic message, the unsolicited service $20 positive response message shall be delayed until after the 
multi-frame message (reception or transmission) has completed. 
8.5.2 Request Message Definition (Table 75). 
Table 75: Request Message Definition 
Data Byte Parameter Name 
Cvt 
Hex Value Mnemonic 
#1 
returnToNormalMode Request Service Id 
M 
20 
SIDRQ 
8.5.2.1 Request Message Sub-Function Parameter $Level (LEV_) Definition. 
Because this service is 
defined as a single operation, there are no sub-parameters required or valid for the request message. 
8.5.2.2 Request Message Data Parameter Definition. 
There are no data parameters used by this service.
 
8.5.3 Positive Response Message Definition (Table 76). 
Table 76: Positive Response Message Definition