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 48 of 336 
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Diagnostic
Application
GMLAN
Handler
Tester
app. triggered
diagnostic VN
active
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diagnostic
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active
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1) request
response
2) request
(requires diagnostic mode)
3) request
(AllNodes TesterPresent)
4) request
(stops diagnostic mode)
response
response
ECU_IN_STANDBY
COMM_INIT
COMM_ENABLED
COMM_ACTIVE
Communication State
COMM_ENABLED
ECU_READY
Reset and
disable Timer
initally active
diagnostic
VN active
Start Timer
Reset and
disable Timer
Start Timer
Timeout
4-8 sec
VN deactivated
diagnostic mode
deactivated
initally active
diagnostic VN
deactivated
8 sec
Activate VN
DIAG_DISABLED
DIAG_ACTIVE
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Application State
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DIAG_MODE_ACTIVE
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Note:
It is assumed that the Application Triggered Diagnostic VN is the only active VN. 
Figure 15: Diagnostic Local VN - Activation and Deactivation Example 
6 Wake-up Requirements and Timing Parameters 
6.1 Wake-up Requirements. 
The GMLAN communication strategy supports node communication shut down 
and also supports the possibility for a node to enter a low power state when its functionality is not needed. If a 
diagnostic tester wishes to communicate with a node which is in a low power state, or a state where 
communications capabilities have not been established (see note below), then the tester must first issue a 
wake-up. The wake-up mechanism for the Single Wire CAN (SWCAN) low speed link is the High Voltage 
Wake-up message. The allowable methods for performing a wake-up on the dual wire CAN links are defined in 
GMW3104 and include: 
Note:
See section on diagnostics and node management for more information about a nodes communication 
states. 
Note:
See the GMLAN Communication Strategy Specification (GMW 3104) for more information on the High 
Voltage Wake-up message. 
1. Use of a wake-up wire. 
2. Wake-up on bus activity. 
3. Wake-up on discrete Accessory or Ignition power mode information. 
The GMLAN communication strategy does not require gateways to cascade wake-up requests to all subnets 
that it supports. The strategy also allows for wake-up mechanisms which are not accessible to a tester (e.g., 
use of a wake-up wire). The InitiateDiagnosticOperation ($10) service provides a mechanism for a tester to 
request a gateway to generate a wake-up on all GMLAN subnets that it connects to where at least one Virtual 
Network is supported. 
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