RAW, yes, but really depends on the scenario (and the DM)
While sometimes agreed to, and even remarked in unofficial Tweets, most of the DM's I've been with only use passive as passive and not as a baseline. It sucks, because I have a character with a passive 21 perception. Yet when asked to roll, he is not always that successful.
Are you working together, or are you splitting up the work?
Part of the rules on helping someone states,
Moreover, a character can help only when two or more individuals working together would actually be productive. Some tasks, such as threading a needle, are no easier with help.
For someone to help in a search, it would typically be something like, "I"ll watch the left, you watch the right." But that doesn't make my looking to the right any easier or better. I have less to look at, but I'm only searching half of the possibilities. This is like, "I'll search the dresser, you search the bed." You're not helping me search the bed, you're just limiting the job I need to do. And if you're giving me advantage, that means you're not rolling to look for your half of the job.
So in cases like that, Help doesn't help. To help a search, you'd have to keep double checking someone's work; "Did you look in that tree? Along that branch? Behind that bush? Under those leaves?..."
Are you repeatedly doing the skill, or just once thoroughly?
Under passive checks, it lists out when to use them:
Such a check can represent the average result for a task done repeatedly, such as searching for secret doors over and over again, or can be used when the DM wants to secretly determine whether the characters succeed at something without rolling dice, such as noticing a hidden monster.
When a DM asks for a roll to see if you find a secret door, you're going to search the room one time to the best of your ability. Why would you search "over and over" if you don't know what you're looking for, or if it even exists. Now, on the other hand, if you say, "I know the villain escaped from this locked, windowless room. There has to be a secret door and I'm not going to stop until I find it," then maybe a passive check would be better (so long as you actually have a good passive score and they weren't teleported out). This is more akin to older editions, "take 10" or "take 20".
Even then, no DM I know uses passive that way. They let the player make multiple rolls (with possible advantage), but increase the DC each time.
For instance, walking through a forest, you are not repeatedly checking the same bit of path over and over, you are watching your current area until you walk past and then searching the next.
A place where "over and over" might get the Help action would be something like the Rubik's Cube. You keep trying to solve it, and over time, you learn patterns. Someone else could be over your shoulder saying, "Hey, did you notice that no matter how much you twist the cube, the color combinations of the corners never change? And that in the center, yellow is always opposite blue? That means we only really need to line up edges."
So again, yes, but it really depends on if what you're doing is "passive"
- Tracking is not passive. You're actively looking for clues, but in walking you may passively notice blood on a leaf.
- Looking for secret doors is not passive. You're actively looking, but in looking under the bed for loot you may passively find a secret door.
- Picking a lock is not passive. You're trying once to the best of your ability to get the tumblers just right. Someone over your shoulder is not going to help "feel out" the lock.
- Remembering history and be active or passive. Player one reads a passage and muses, "I recall there was some legend about the lighthouse on the hill," and player two can Help (if they are also proficient in History) and say, "Yeah, I heard stories about it as a kid." Then they compare notes and gain advantage.
