National Instruments CAN 372139B-01 - Manual (Page 154)

Chapter 5 Automotive Diagnostic Command Set API for LabVIEW
Automotive Diagnostic Command Set User Manual 5-128 ni.com
OBD Request Emission Related DTCs During Current Drive Cycle.vi
Purpose
Executes the OBD Request Emission Related DTCs During Current Drive Cycle service.
Reads the emission-related Diagnostic Trouble Codes (DTCs) that occurred during the
current (or last completed) drive cycle.
Format
Input
DTC descriptor is a cluster that describes the DTC records the ECU
delivers:
DTC Byte Length indicates the number of bytes the ECU sends
for each DTC. The default is 2.
Status Byte Length indicates the number of bytes the ECU sends
for each DTC’s status. The default is 0 for OBD.
Add Data Byte Length indicates the number of bytes the ECU
sends for each DTC’s additional data. Usually, there is no
additional data, so the default is 0.
Byte Order indicates the byte ordering for multibyte items:
0: MSB_FIRST (Motorola) (default)
1: LSB_FIRST (Intel)
This VI interprets the response byte stream according to this description
and returns the resulting DTC records in the DTCs cluster array.
diag ref in specifies the diagnostic session handle, obtained from Open
Diagnostic.vi and wired through subsequent diagnostic VIs. Normally, it is
not necessary to manually manipulate the elements of this cluster.