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

Tester Transmit
ECU #1 Transmit
ECU #2 Transmit
ECU #3 Transmit
Tester NWL
P2
CT
150
0
P2
CT
150
0
P2
CT
150
0
P2
CT
150
0
con
ind
ind
ind
req
Request
USDT-SF
USDT-CF
USDT-SF
USDT-FF
Start (150)
Restart(150)
Restart(150)
Restart(150)
Next Request
Tester Transmit
ECU #1 Transmit
ECU #2 Transmit
ECU #3 Transmit
USDT-FC
USDT-CF
. . .
USDT-FC
Tester NWL
P2
CT
150
0
P2
CT
150
0
P2
CT
150
0
P2
CT
150
0
req
con
ind
ind
ind
ind
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GM WORLDWIDE ENGINEERING STANDARDS 
GMW3110 
© Copyright 2010 General Motors All Rights Reserved 
February 2010 
Page 54 of 336 
of responding ECUs and all expected response messages are completely received then the tester can 
immediately transmit the next request message. 
Note:_The_indication_of_a_successful_reception_of_a_multi-frame_response_message_does_not_restart_the_P2_CT'>Note:
The indication of a successful reception of a multi-frame response message does not restart the P2
CT
application timer in the tester. Only the start of the multi-frame response message indicated via the first frame 
indication (N_USData_FF.ind) is relevant for the restart of the P2
CT
timer. 
Figure 21: Tester P2
CT
 Timing Parameter Definition - Multiple UUDT Response Messages 
Note:
The timing handling of the tester that applies to subsequent UUDT messages, optionally following the 
first UUDT message is not shown in the figure above. 
In Figure 21, the tester transmits a functionally addressed request message (e.g., $A9) and three ECUs 
respond. Two ECUs respond with two UUDT messages and one ECU responds with one UUDT message. In 
this example the tester either waits for a P2
CT
timeout and the completion of all UUDT response messages 
(number of responding ECUs not known), or only for the completion of all UUDT response messages (number 
of responding ECUs known). 
Note:
Only the successful reception of the first UUDT response message of each ECU following the request 
message restarts the P2
CT
application timer in the tester. 
6.2.2 Application Timing Parameter P2
CE
*/P2
CT
*Definition. 
If an ECU cannot respond with its final USDT 
response message or its first UUDT response message following a service $AA or $A9 request message 
within the required P2
CE
timing window as specified in paragraph 6.2.1.1, then the ECU can indicate to the 
tester that an enhancement of its response timing parameter to P2
CE
* is required. This can be done by sending 
a negative response message with response code $78 (RequestCorrectlyReceived-ResponsePending) within 
the initial P2
CE
timing window as defined below. Upon receiving a negative response with response code $78, 
the tester shall modify its normal P2
CT
timing to the enhanced P2
CT
* timing as defined below.