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

CT
, shall restart the P2
CT
application timer in the tester with the 
Request
SF-RC78
SF-RC78
USDT-FF
. . .
USDT-CF
USDT-CF
USDT-FC
USDT-FC
ECU NWL
Tester NWL
req
con
ind
req
con
ind
req
con
ind
req
ind
con
ind
P2
CE
100
0
P2
CE
P2CE*
0
P2
CE
P2CE*
0
Request
SF-RC78
UUDT
UUDT
Tester Transmit
ECU Transmit
ECU NWL
Tester NWL
req
con
ind
req
con
ind
req
con
ind
req
con
ind
. . .
...
P
X
0
P2
CE
100
0
P2
CE
P2CE*
0
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GM WORLDWIDE ENGINEERING STANDARDS 
GMW3110 
© Copyright 2010 General Motors All Rights Reserved 
February 2010 
Page 57 of 336 
current active reload value, which can either be the normal P2
CT
timing parameter value (normal timing), 
or, if at least one ECU requested an enhanced response timing, the P2
CT
* timing parameter value 
(enhanced timing). 

The tester shall keep track of the ECUs which requested an enhanced response timing. The tester has to 
build an ECU list which contains unique identifications of all ECUs which requested an enhanced response 
timing, because the tester has to know the ECUs which requested enhanced response timing in order to 
determine when the normal P2
CT
timing parameter reload value should be re-enabled. The normal P2
CT
parameter is re-enabled when all ECUs which have requested enhanced response timing have responded 
with a single frame response message, the first frame of a multi-frame response message or the first 
USDT response message. The list shall be built based on the negative response messages with response 
code $78 sent by the ECU(s). 

The tester shall be able to transmit functionally addressed TesterPresent request messages while 
performing the enhanced response timing (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
.)