When a process model depends on the value of a variable being set by another process, a synchronous subprocess should be used. This ensures that the calling process (VIM Update Vehicle) will wait for the subprocess (VIM Get Service Date) to complete and set the necessary pv!serviceDate value before continuing. The subprocess node should be configured with input and output variables to pass the pv!vehicleId and receive the pv!serviceDate.

References

Appian Documentation: Subprocess Node