National Instruments CAN 372139B-01 - Manual (Page 151)

Chapter 5 Automotive Diagnostic Command Set API for LabVIEW
© National Instruments Corporation 5-125 Automotive Diagnostic Command Set User Manual
OBD Request Emission Related DTCs.vi
Purpose
Executes the OBD Request Emission Related DTCs service. Reads all emission-related
Diagnostic Trouble Codes (DTCs).
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.
error in is a cluster that describes error conditions occurring before the VI
executes. If an error has already occurred, the VI returns the value of the
error in cluster to error out.