National Instruments CAN 372139B-01 - Manual (Page 213)

Chapter 6 Automotive Diagnostic Command Set API for C
© National Instruments Corporation 6-49 Automotive Diagnostic Command Set User Manual
DTCDescriptor
A struct that describes the DTC records the ECU delivers:
typedef struct {
long DTCByteLength;
long StatusByteLength;
long AddDataByteLength;
unsigned short ByteOrder;
} TD3;
DTCByteLength indicates the number of bytes the ECU sends for each DTC. The
default is 2.
StatusByteLength indicates the number of bytes the ECU sends for each DTC’s
status. The default is 1.
AddDataByteLength indicates the number of bytes the ECU sends for each DTC’s
additional data. Usually, there are no additional data, so the default is 0.
ByteOrder indicates the byte ordering for multibyte items:
0: MSB_FIRST (Motorola) , default
1: LSB_FIRST (Intel)
This function interprets the response byte stream according to this description and
returns the resulting DTC records in the
DTCs struct array.
Output
DTCs
Returns the resulting DTCs as an array of structs:
typedef struct {
unsigned long DTC;
unsigned long Status;
unsigned long AddData;
} TD4;
DTC is the resulting Diagnostic Trouble Code. For the default 2-byte DTCs, use
ndDTCToString to convert this code to readable format as defined by SAE J2012.
Status is the DTC status. Usually, this is a bit field with following meaning:
Bit Meaning
0 testFailed
1 testFailedThisMonitoringCycle
2 pendingDTC
3 confirmedDTC
4 testNotCompletedSinceLastClear
5 testFailedSinceLastClear