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

CT
to the enhanced P2
CT
* timing parameter value and stores an ECU 
identification that the final response of this ECU is pending. When the ECU finally starts to respond (first UUDT 
message), the tester deletes the ECU identification in its internal list of pending ECU responses. At the point in 
time when the last ECU which requested an enhanced response timing finally starts its response message, the 
tester re-enables the normal P2
CT
reload value for its P2
CT
timer. Any subsequent start of an ECU response 
message (first UUDT message of this ECU) during an active enhanced response timing P2
CT
* forces the tester 
to restart its P2
CT
timer as defined for the general handling of P2
CT
using the currently active reload value. 
Request
SF-RC78
SF-RC78
UUDT
UUDT
SF-RC78
Start (150)
Restart (P2C*)
Restart (P2C*)
Restart (P2C*)
Restart (150)
UUDT
Restart (P2C*)
Restart (150)
Normal Timing
active
Enhanced Timing
activated
Normal Timing
re-activated
Normal Timing
Normal Timing
Enhanced Timing
UUDT
UUDT
ECU #1 Transmit
Tester Transmit
Tester NWL
ECU #2 Transmit
ECU #3 Transmit
150
0
P2
CT
P2
CT
150
0
P2
CT
P2CT*
0
P2
CT
P2CT*
0
P2
CT
P2CT*
0
P2
CT
P2CT*
0
P2
CT
150
0
req
con
ind
ind
ind
ind
ind
ind
ind
Tester internal status:
RC78PendingEcuCounter
RC78PendingEcuList
P2CTReloadValue
+1=1
ECU#1
5100
-1=0
ECU#1
ECU#3
150
0
150
no change
no change
no change
+1=2
ECU#1
ECU#3
5100
-1=1
ECU#1
ECU#3
no change
no change
no change
no change
no change
no change
no change
ind
last
last
last
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GM WORLDWIDE ENGINEERING STANDARDS 
GMW3110 
© Copyright 2010 General Motors All Rights Reserved 
February 2010 
Page 60 of 336 
6.2.2.3 Enhancement of P2
CE
*/P2
CT
* During A Programming Session (Tables 31 and 32). 
During a 
programming session enabled via the sequence defined in the Programming Procedure it is helpful to further 
enhance the P2
CE
*/P2
CT
* timing to allow ECUs to process, e.g., an 
Erase Flash Memory
command which can 
take longer than 5000 ms without having to send any additional negative response messages with response 
code $78 (following the initial negative response message with response code $78). 
The further enhancement of P2
CE
*/P2
CT
*applies to the ECU(s) and the tester only during an enabled 
programming session. 
Table 31: ECU P2
CE
* Timing Parameter Value During an Active Programming Session 
Parameter 
Description 
Minimum 
(Cemin*) 
 [ms] 
Maximum 
(Cemax*) 
[ms] 
P2
CE
* 
Enhanced response timing for a single ECU during an active 
programming session. 
0 
30000 
Table 32: Tester P2
CT
* Timing Parameter Value During an Active Programming Session 
Parameter 
Description 
Minimum 
(Cmin) 
 [ms] 
Maximum 
(Cmax) 
[ms] 
P2
CT
* 
Enhanced response timing value for tester P2
CT
timer during an 
active programming session. 
30200 
N/A 
Note 1
Note 1:
The value that a tester uses for P2
CTmax
* is left to the discretion of the tester as long as it is greater than P2
CTmin
*. 
The handling which applies to those timing parameter values is identical to the general P2
CE
*/P2
CT
* handling. 
The only differences are the values to be fulfilled in the ECU (timing requirement) and in the tester (timeout). 
6.2.3 Application Timing Parameter Definition for UUDT Response Messages. 
The diagnostic services 
ReadDiagnosticInformation ($A9) and ReadDataByPacketIdentifier ($AA) use UUDT messages to transmit the 
requested data to the tester. UUDT messages use a different CAN Identifier than USDT messages, therefore 
they can interleave multiple frame USDT messages. UUDT messages are primarily used for the transmission 
of dynamic data. 
An ECU has to comply with the general request/response scheme and therefore has to respond with the first 
UUDT response message after the successful reception of the request message. The timing of this UUDT 
response message shall be as described for the P2
CE
application timing parameter. Following this initial 
response the ECU can start to transmit the requested data using UUDT messages. 
The definition of the timing that applies to the subsequent UUDT response messages can be found in the 
description of the diagnostic services ReadDiagnosticInformation ($A9) and ReadDataByPacketIdentifier 
($AA). 
If the ECU cannot respond to the diagnostic service $A9 or $AA within the P2
CE
timing, because of, e.g., 
internal checks based on the requested data than it can request an enhanced response timing as defined in 
paragraph 6.2.2. 
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