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

C
2
= Certain sub-function parameters may be supported on non-programmable ECUs to support 
manufacturing needs of the ECU supplier or the vehicle assembly plant. 
4.3 Diagnostic Communication Implementation Rules. 
In applying the rules which follow, a diagnostic 
request is considered in process, until the node has fulfilled one of the following (depending on the specific 
service requested): 

The ECU sent the last consecutive frame of an USDT multi-frame positive response. 

The ECU sent an USDT negative response message indicating there is no positive response forthcoming 
(response code other than $78). 

The ECU sent an USDT single frame positive response message. 

The first (or only) UUDT response is received (for services $AA and $A9). 
Note:
Application timing requirements for UUDT diagnostic responses provided via services $A9 and $AA are 
specified in each respective service within this specification. Reference the descriptions of these services for 
additional detail. 
4.3.1 Tester Rules. 
1. A tester is not allowed to send a physically addressed request any time a previous physically addressed 
request is in process. 
2. A tester is not allowed to send a physical request any time a functional request has been received that will 
result in a response, and the response to the functional request is in process. 
3. A tester is not allowed to send a functional request that results in a response if a previous physically 
addressed request is in process. 
--``,,``````,``,,``,,,`,`,`,,-`-`,,`,,`,`,,`---
CameraLoops.com

---

GM WORLDWIDE ENGINEERING STANDARDS 
GMW3110 
© Copyright 2010 General Motors All Rights Reserved 
February 2010 
Page 20 of 336 
4. A tester is not allowed to send a functional request that results in a response if a previous functionally 
addressed request is in process. 
5. After sending a functionally addressed request which will result in a response, a tester is not allowed to 
send a second functionally addressed request that does 
not
result in a response (e.g., TesterPresent 
request) until at least 30 ms has elapsed after sending the first request. 
6. A tester shall wait a minimum of 30 ms after sending a functionally addressed request that does not result 
in a response before sending another functionally addressed request message. 
7. A tester can send a functionally addressed request message that does not result in a response (e.g., 
functional tester present) at any point in time during which the ECU is in the process of receiving or 
responding to a physically addressed diagnostic request. (In other words the functionally addressed tester 
present request may even interleave the transmission of frames of a multi-frame physical request 
message or a multi-frame physical response message.) 
8. A tester may also send a diagnostic physical request immediately following a diagnostic functional request 
as long as the functional request does not require a response. 
Table 7 provides an additional overview about the required handling in the tester also taking into consideration 
the node specific rules given in paragraph 4.3.2. The