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

 
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03 
enableDTCsDuringDevCntrl
This level shall be used to allow DTC algorithms to continue to execute while the 
DeviceControl ($AE) service is active. This request shall have to be made prior to 
activating DeviceControl or the request shall be rejected. If this service and level are not 
requested before entering DeviceControl, then DTCs shall be inhibited while 
DeviceControl is active. (See the $AE service for further details). 
Note:
If another diagnostic service is requested which disables DTCs (after the request is 
sent to allow DTCs to run during DeviceControl) then the DTCs shall become inhibited 
and remain inhibited until after a TesterPresent timeout occurs or a $20 service is 
requested. 
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04 
wakeUpLinks
This level shall cause a gateway ECU to initiate the appropriate wake-up sequence on all 
GMLAN subnets that it is connected to (provided that a given subnet has a wake-up 
mechanism defined). 
Note: 
The rules for sending a wake-up as defined in GMW 3104 - GMLAN 
Communications Strategy Specification still apply (e.g., the strategy specification restricts 
wake-up requests to have a minimum time interval between them. If a diagnostic request 
is received to initiate a wake-up and the minimum interval has not expired, then the ECU 
shall send the positive response message back to the tester without initiating another 
wake-up). 
If a GMLAN subnet uses a shared local input as a wake-up wire and the shared local 
input has to remain asserted to keep communications active, then the gateway device 
shall ensure that the wake-up wire is asserted while the gateways diagnostic VN is active. 
Note:
An example of the shared local input wake-up mechanism described above would 
be a gateway that is connected to both the single wire CAN link and a dual wire CAN link. 
In this example, the gateway uses a relay to switch power to the other devices on the dual 
wire CAN subnet. For normal operations the gateway would receive the High Voltage 
wake-up on the single wire CAN bus and then enable the relay to provide power to the 
dual wire devices. If the ECU receives a request for this service with the wakeUpLinks 
($04) sub-function parameter, then the ECU would ensure that the relay providing power 
to the dual wire link ECUs remains enabled as long as the diagnostic VN is active in the 
gateway (or longer if the ECU would otherwise keep the relay enabled for normal 
functionality after the diagnostic VN is no longer active). 
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