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 238 of 336 
a CTS or SSTS. The type of DeviceControl restrictions enforced (service or Assembly plant) shall remain 
unaffected if a DeviceControl restriction is exceeded. Refer to the SecurityAccess ($27) and the 
ReturnToNormalMode ($20) service descriptions within this specification for additional details on how the type 
of DeviceControl restriction is determined. 
Upon receiving a DeviceControl request message, an ECU shall normally inhibit the setting of Diagnostic 
Trouble Codes (DTCs). This is done to prevent DTCs from setting as a result of the off board testers 
modifications to the normal output control algorithms. Once DTCs are inhibited, they will remain inhibited until 
a TesterPresent ($3E) timeout occurs or until a ReturnToNormalMode ($20) service request is received. In 
order to facilitate vehicle manufacturing needs to quickly diagnose vehicles during the assembly process, 
certain ECUs shall be required to keep diagnostic algorithms active while DeviceControl functions are active. 
The tester can keep the diagnostic algorithms active during DeviceControl by sending the appropriate 
InitiateDiagnosticOperation (service $10) request prior to activating DeviceControl. See service $10 for more 
information. 
This service requires that a TesterPresent ($3E) service be sent at least once every P3
C
ms or the device will 
cancel all active device controls and resume normal control of its outputs.
If a device has any CPIDs which are used during SPS programming, are required for theft related functions 
(e.g., deterrent key re-learn), or are somehow safety related, the device must then support the SPS security 
levels of the SecurityAccess ($27) service. 
A given device control is allowed to be packed into more than one CPID if necessary to meet test timing 
requirements. If a given device control is in more than one CPID, the actions requested by the last message 
containing that device control shall remain active. 
All device controls shall be terminated if any of the following occur: 

A TesterPresent (P3
C
) time-out occurs. 

A device control request is received with a CPID number of $00. 

A device control limit is exceeded on any active device control. 

A ReturnToNormalMode($20) request message is received. 

The device is powered down. 
An individual device control can be terminated in the following manner: 
1. A device control request is received with the same CPID number and the enabling criteria turned off. 
2. Any of the criteria listed above to cancel all device controls are met. 
Note: 
ECU normal control algorithms determine the state of a given output once the appropriate DeviceControl 
has been terminated (unless the termination is the result of an ECU power down). 
This service shall be allowed while other diagnostic services are also active (e.g., diagnostic periodic data 
scheduler, etc.) If data is requested which includes the state of a node
’s outputs while those outputs are under 
device control, the data representing the output state shall reflect its commanded state. In other words, if a 
node
’s normal output control algorithm is commanding an output to the off state and a DeviceControl request is 
processed which turns that same output to the on state, periodic or other data containing the state of the 
output shall indicate that the output is on. 
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