Страница 1 мировой engineering стандарты общая спецификация

8.18 ReadDiagnosticInformation ($A9) Service. 
This service allows a tester to read the status of
node-resident Diagnostic Trouble Code (DTC) information from any controller, or group of controllers within a
vehicle. This service allows the tester to do the following:
1. Retrieve the status of a specific DTC and FaultType combination.
2. Retrieve the list of DTCs that match a tester defined DTC status mask.
3. Enable a node resident algorithm which periodically calculates the number of DTCs that match a tester
defined DTC status mask. The ECU shall send a response message each time the calculation yields a
different result than the one calculated the previous time.
8.18.1 Service Description. 
This service uses a sub-parameter to determine which type of DTC information is
being requested by the tester. The message number in the UUDT response message shall be the same as the
sub-parameter byte in the request message. UUDT message numbers ranging from $80 thru $8F have been
reserved for UUDT diagnostic responses for this service and shall not be used for UUDT responses to the $AA
service. ECU timing requirements for transmitting the UUDT responses are defined in the description sections
below.
Note: 
An ECU will not transmit a USDT-SF message to positively acknowledge a tester’s service $A9 request.
However, if conditions necessitate, a $7F negative response message (USDT-SF) may be sent in response to
the tester’s request (see supported negative responses within this service description for more details).
It shall be possible for a tester to send a request to retrieve the status of a single DTC and Failure type
combination, or send a request to determine which DTCs match a tester defined status mask, while the node
resident send on change DTC count algorithm is running. However, to ease the burden on an ECU, a node
may temporarily suspend the DTC count algorithm while processing a request of the other types.