National Instruments CAN 372139B-01 - Manual (Page 55)

Chapter 5 Automotive Diagnostic Command Set API for LabVIEW
© National Instruments Corporation 5-29 Automotive Diagnostic Command Set User Manual
code is the error code number identifying an error. A value of 0
means success. A negative value means error: the VI did not
execute the intended operation. A positive value means warning:
the VI executed intended operation, but an informational warning
is returned. For a description of the code, wire the error cluster to
a LabVIEW error-handling VI, such as the Simple Error
Handler.
source identifies the VI where the error occurred.
Description
For the VW TP 2.0, you must periodically maintain the connection link to the ECU so that
the ECU does not terminate it.
This VI sends a Connection Test message to the ECU and evaluates its response, performing
the steps necessary to maintain the connection.
There is no equivalent for the ISO TP (ISO 15765-2), as the ISO TP does not use a special
communication link.