25.06.2020
WORLDWIDE ENGINEERING STANDARDS General Motors Local Area Network Enhanced Diagnostic
Test Mode Specification
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February 2010
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dataIdentifier to a secured ECU (security code has not been entered) and
verify the negative response
($7F $3B $31 - RequestOutOfRange).
2. Send a $3B message with a security code required dataIdentifier and associated data bytes after the
dataIdentifier when the security code has been entered and verify the positive response.
3. Repeat steps 1 and 2 for each DID that requires the security code.
8.14.8 Tester Implications.
This service should be used with physical addressing.
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GM WORLDWIDE ENGINEERING STANDARDS
GMW3110
8.15 TesterPresent ($3E) Service.
This service is used to indicate to a node (or nodes) that a tester is still
connected to the vehicle and that certain diagnostic services that have been previously
activated are to remain
active. Some diagnostic services require that a tester send a request for this service periodically in order to
keep the functionality of the other service active. Documentation within this specification
of each diagnostic
service indicates if a given service requires the periodic TesterPresent request to remain active.
8.15.1 Service Description.
This service keeps other diagnostic services active by resetting the diagnostic
timer (TesterPresent_Timer) each time a request for this service is received. A portion
of the ECU diagnostic
application executes in the background that modifies and tests the value of the timer (modification based on
the processing loop time). When the value of the TesterPresent_Timer meets or exceeds the value of the P3
C
application timer, a TesterPresent or P3
C
timeout occurs.
Note:
See the paragraphs within this specification on application timing requirements
for more information on
P3
C
.
When a P3
C
timeout occurs, the node shall execute the same logic that would be executed if a
ReturnToNormalMode ($20) service request was received. This includes
the transmission of a
ReturnToNormalMode positive response message. (See note below) Nodes are required to time out no sooner
than P3
C
and no later than P3
Cmax
.
Note:
The unsolicited service $20 positive response is only sent if programming
mode was not active prior to
the TesterPresent timeout. See service $A5 for more information on programming mode.
There shall only be a response to a request for this service if the request is physically addressed.
Note:
Receiving a TesterPresent request message shall not put a node into a diagnostic mode (i.e., the
TesterPresent_Timer_State shall not be set to ACTIVE by this message; see pseudo code).
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