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 61 of 336 
6.2.4 Application Timing Parameter P3
C
Definition (Table 33).
The timing parameter P3
C
is defined to be 
the maximum time between two consecutive TesterPresent ($3E) service request messages. TesterPresent 
request messages shall be sent by the tester within P3
C
when the tester desires certain previously activated 
diagnostic services to remain active within one or multiple ECU(s). The tester shall always use a P3
C
value 
less than the specified P3
Cnom
value. 
Note:
It is recommended that the tester transmits a TesterPresent request message every 2 s. 
Note:
See the sections of this specification describing the individual diagnostic services to determine which 
service requires a TesterPresent service to remain active. 
Table 33: P3
C
 Timing Parameter Value 
Parameter 
Description 
Nominal 
(Cnom)
[ms] 
Maximum
(Cmax) 
[ms] 
P3
C
Maximum time between TesterPresent requests sent by the 
tester. 
5000 
5100 
TesterPresent service request messages can be physically or functionally addressed. Each ECU shall be able 
to receive and process a functionally addressed TesterPresent request message (single frame message with 
AllNode CAN Id and valid extended address, e.g., AllNode extended address $FE) in between the 
reception/transmission of a physically addressed single or multi-frame request/response message and during 
an active enhanced response timing in order to reset its P3
C
timer. 
Note:
This functionality shall keep a node in a previously activated diagnostic mode of operation if the 
transmission/receipt of the multiple-frame message or the preparation of the final response message during an 
active enhanced response timing takes longer than P3
C
. 
The ECU shall recognize that a P3
C
timeout (also referred to as TesterPresent timeout) has occurred at a time 
greater than or equal to P3
Cnom
and less than or equal to P3
Cmax
: