"pasar de frenada/venir~ir de pasada" means that you/someone goes/went/will go to somewhere for doing something and it was just made for a moment, not during a long time.
And that phrase implies that you/someone does/did/will do that just before doing something (and that's why that phrase is used when someone has to do other things planned beforehand and he/she does something else among those other things he planned to do) .
It's always said in past tense, because it's used for giving an explanation or giving information about something that you/someone did.
For example:
Ayer fui a la estación de servicio a cargar nafta, pasé de frenada por la casa de mi hermana para saludarla, y finalmente me fui de vacaciones.
I hope I'd helped you!