Purpose

Executes the UDS TesterPresent service. Keeps the ECU in diagnostic mode. Format

Input

diag ref in specifies the diagnostic session handle, obtained from Open Diagnostic on CAN FD.vi or Open Diagnostic on IP.vi and wired through subsequent diagnostic VIs. Normally, it is not necessary to manually manipulate the elements of this cluster.
response required? indicates whether the ECU answers this service (TRUE, default) or not (FALSE). In the latter case, success? is TRUE.
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.
status is TRUE if an error occurred. This VI is not executed when status is TRUE.
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.

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 UDS TesterPresent.vi within the ECU timeout period if no other service is executed.