8.18.1.1 Retrieving the Status of a DTC and Failure Type Combination.
A tester can retrieve the status of a
specific DTC and DTCFailureTypeByte (symptom) combination by sending a request for this service with the
sub-parameter set to readStatusOfDTCByDTCNumber ($80). The response to this request is a UUDT
message (message number = $80) containing the two byte DTC Number, the one byte DTCFailureTypeByte,
and the one byte DTCStatusByte. The definitions of the DTCFailureTypeByte and the DTCStatusByte can be
found in Appendix E.
If the ECU diagnostic application determines that the tester request is NOT acceptable (e.g., incorrect format),
the ECU shall return an appropriate USDT-SF negative response within the P2
C
time window followed by NO
($80) UUDT message.
8.18.1.2 Retrieving the List Of DTCs That Match A Tester Defined Status Mask.
The tester can retrieve a
list of DTC numbers and DTCFailureTypes which satisfy a tester defined status mask by sending a request
with the sub-parameter byte set to readStatusOfDTCByStatusMask ($81). Nodes shall be able to mask on
more than one bit of the status byte field at a time via a logical
OR-ing
operation, making it possible for the
tester to request a node to transmit all DTCs that are
current
OR
history
OR , etc., with a single request. If a
tester specifies a status mask that contains bits that the node does not support, then the node shall process
the DTC information using only the bits that it does support. In response to the tester’s request, the ECU shall
return a UUDT message to the tester for each DTC and DTCFailureTypeByte combination that satisfies the
masking criteria specified by the tester (refer to diagram below for response timing). The UUDT response
message(s) shall contain the 2-byte DTC number, the one byte DTCFailureTypeByte, and the one byte
DTCStatusByte. Once all DTCs satisfying the tester-specified masking criteria have been transmitted, the ECU
shall transmit a special endOfDTCReport UUDT message to flag the end of the transmission. Refer to the
corresponding response message definition table below for formatting details regarding the endOfDTCReport
message. If no DTC/DTCFailureTypeByte combinations match the masking criteria, then the ECU shall only
transmit the endOfDTCReport message in response to the tester’s request.
The ECU diagnostic application shall transmit the first UUDT response (or USDT-SF negative response) within
P2
C
of receiving the tester request. Once the first UUDT response has been sent, each subsequent UUDT
response message(s) shall be transmitted within P2
C
from the previously transmitted ($81) UUDT response
message.
Note:
The P2
C
timing is the maximum interval that an ECU should send the UUDT responses. It is acceptable
to send them at a rate faster than P2
C
.
If the ECU diagnostic application determines that the tester request message is acceptable, but cannot
transmit the first UUDT response message within the P2
C
time window, it shall transmit a $7F $A9 $78
RequestCorrectlyReceived-ResponsePending to the tester to invoke enhanced timing P2
C
*. Once the ECU is
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