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

6.2.2.1 ECU Timing Parameter P2
CE
* (Table 29 and Figures 22 thru 25). 
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 normal P2
CE
timing window as specified in paragraph 6.2.1.1, then it shall perform 
the following handling: 

The ECU shall respond with a negative response message (single frame message) with response code 
$78 - RequestCorrectlyReceived-ResponsePending within normal P2
CE
timing as defined in paragraph 
6.2.1.1. This forces the tester to set its P2
CT
timing parameter value to P2
CT
*. See paragraph 6.2.2.2. 

If the ECU requires more than P2
CE
* to perform the requested action, then it shall repeat the negative 
response message with response code $78 prior to expiration of P2
CE
*. This shall continue until the ECU 
Next Request
Request
UUDT
UUDT
UUDT
UUDT
UUDT
Start (150)
Restart(150)
Restart(150)
Restart(150)
last frame
last frame
last frame
Tester NWL
con
ind
ind
ind
req
ind
ind
Tester Transmit
ECU #1 Transmit
ECU #2 Transmit
ECU #3 Transmit
Next Request
responding ECUs known
responding ECUs not known
P2
CT
150
0
P2
CT
150
0
P2
CT
150
0
P2
CT
150
0
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