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 55 of 336 
is capable of sending the final USDT response (positive response or negative response with a response 
code other than $78) or the first UUDT response message. 

For its final USDT response message or UUDT response message the ECU has to make sure that the 
single frame response message (positive or negative response other than response code $78), the first 
frame of a multi-frame response message or the first UUDT response message is completed (transmitted 
on to the CAN bus) within the last requested P2
CE
*. 

The ECU shall be able to receive and process a functionally addressed TesterPresent service request 
messages while it has activated the enhanced response timing and prepares the final response message. 
Note:
This functionality shall keep a node in a previously activated diagnostic mode of operation if the 
preparation of the final response message takes longer than P3
C
. 
Table 29: ECU P2
CE
* Timing Parameter Value 
Parameter 
Description 
Minimum 
(CEmin*) 
[ms] 
Maximum 
(CEmax*) 
[ms] 
P2
CE
* 
Enhanced response timing for a single ECU 
0 
5000 
Note 1
Note 1:
OBD/EOBD devices are required to support the timing value P2
CE*
as specified in ISO15031-5 (referred to as P2*
CAN
in 
ISO 15031-5) for emission related services. An OBD/EOBD device may choose to use a single value for P2*
CE
for both emission related 
and enhanced diagnostic services provided that the maximum value used is not greater than the value specified in this table.