National Instruments CAN 372139B-01 - Manual (Page 99)

Chapter 5 Automotive Diagnostic Command Set API for LabVIEW
© National Instruments Corporation 5-73 Automotive Diagnostic Command Set User Manual
Output
diag ref out is a copy of diag ref in. You can wire it to subsequent
diagnostic VIs.
success? indicates successful receipt of a positive response message for
this diagnostic service.
error out describes error conditions. If the error in cluster indicated an
error, the error out cluster contains the same information. Otherwise,
error out describes the error status of this VI.
status is TRUE if an error occurred.
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
To ensure proper ECU operation, you may need to keep the ECU informed that a diagnostic
session is still in progress. If you do not send this information (for example, because the
communication is broken), the ECU returns to normal mode from diagnostic mode after a
while.
The TesterPresent service is this “keep alive” signal. It does not affect any other ECU
operation.
Keep calling TesterPresent.vi within the ECU timeout period if no other service is executed.