How do I unlock Island Scan in Pokemon Sun and Moon?

The QR Scanner has to reach 100 points before Island Scan appears, and every random code you scan is worth 10 while an official Special code is worth 20, which puts it ten ordinary scans away. It sits in its own slot on the main menu, not inside the Rotom Pokedex. Charges cap at ten and refill one every two hours.

Does Island Scan work on every route?

Each scan searches only the island you are standing on and picks one location there, and which location it picks depends on the day of the week, so on any given day most routes are simply not the spot. Four islands means four targets are live at once. Missing one costs nothing, because the rotation repeats weekly.

Sun & Moon Mahalo Trail

The whole adventure begins on Mahalo Trail, a short walk up to a rickety plank bridge over a gorge. When Nebby wanders out and Spearow swarm, Tapu Koko dives in to save you both and leaves the Sparkling Stone.

Mahalo Trail is in Alola. In the story you arrive from Iki Town to the south and it comes before Route 1.

Pokemon Encounters

No encounters on this map.

This location has no wild Pokemon encounters in the selected game.

ITEMS

Whatever you carry out of Mahalo Trail, the Sparkling Stone matters most, since it later becomes the Z-Ring. An Electric Seed for terrain teams and some Stardust are the only other things worth bagging.

Key item1

Sparkling Stone

Item ball1

Electric Seed

KEY ITEM

Sparkling Stone

From Lillie after saving Nebby from the Spearow

Effect

Required to obtain a Z-Ring.

Key item1

Sparkling Stone

KEY ITEM

Sparkling Stone

From Lillie after saving Nebby from the Spearow

Effect

Required to obtain a Z-Ring.

Item ball1

Electric Seed

ITEM BALL

Electric Seed

Past Plank Bridge on the right, after the bridge is restored

Effect

Held: Consumed on Electric Terrain and raises the holder’s Defense by one stage.

Mahalo Trail Guide

The QR Scanner has to reach 100 points before Island Scan appears, and every random code you scan is worth 10 while an official Special code is worth 20, which puts it ten ordinary scans away. It sits in its own slot on the main menu, not inside the Rotom Pokedex. Charges cap at ten and refill one every two hours.
Each scan searches only the island you are standing on and picks one location there, and which location it picks depends on the day of the week, so on any given day most routes are simply not the spot. Four islands means four targets are live at once. Missing one costs nothing, because the rotation repeats weekly.