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

Start of Diagnostic Request: 
The start of a diagnostic request is defined as reception of either the FirstFrame of a diagnostic request (as 
indicated by the Network Layer), or the reception of a SingleFrame diagnostic request message using the 
defined diagnostic CAN Identifiers. 
Diagnostic Service Finished (successful or with error): 
A diagnostic service is considered finished (or 
completed) if any of the following occurs: 
1. The application receives an error indication from the network layer after the reception of a multi-frame 
message had started. 
2. A request message is successfully received, the application has finished processing the request, and no 
response is required. 
3. A request is received which requires a response, the application has processed the request and

The application receives confirmation from the Network Layer (or Data Link Layer for UUDT responses) 
that the complete diagnostic response message (either USDT single frame, the last frame of a USDT 
multiple frame response, or the last UUDT response message) has been successfully transmitted on the 
bus, 
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GM WORLDWIDE ENGINEERING STANDARDS 
GMW3110 
© Copyright 2010 General Motors All Rights Reserved 
February 2010 
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Note:
Certain diagnostic services such as the $A9 service may send multiple UUDT responses to a single 
request. The service is not considered completed in this case until all of the UUDT responses have been 
confirmed or an error is indicated. 

The application receives an indication from the Network Layer (or Data Link Layer for UUDT responses) 
that an error occurred while transmitting the diagnostic response message on the bus. 
Note:
A functionally performed TesterPresent service is finished after the reception and the processing of the 
request message, because there is no response to a functionally addressed TesterPresent request. 
The next several sections describe the required behavior in each of the states.