How to Catch a Jynx in the Ice Path on "Pokemon HeartGold Version"by Chris Miksen ; Updated September 22, 2017
To get around in “Pokemon HeartGold,” you must take various routes and venture into underground caverns to access different portions of the game. The Ice Path is an underground cave with four floors. You can't run in the Ice Path like you can in other caves and passages in the game. You can only slide on the ice. While on the Ice Path, you have a chance to see Jynx, a Pokemon with Ice and Psychic powers. If you enter the Ice Path at a specific time, your chances of seeing Jynx increase.
Enter the Ice Path during the day. While Jynx appears in the morning, day and night, you have a 10 percent chance of seeing him in the day compared to five percent in morning or at night. The Ice Path is located on Route 44, just south of Mahogany Town.
Venture through the Ice Path. You have a chance of encountering Pokemon each time you take a step in the Ice Path, just like with any underground passage in the game. Although the chances of seeing Jynx are lower than seeing other Pokemon in the Ice Path, you will eventually encounter him.
Fight Jynx with a Level 20-22 Pokemon. Any Pokemon higher than that will likely do too much damage, and you may unintentionally kill Jynx before having a chance to catch her. Do not use a Fire-type Pokemon, because Jynx is considered an Ice-type, which means Fire can one- or two-shot her. Throw a Pokeball once Jynx is low on health.
If Jynx is low on health and you cannot catch her with a Pokeball, use a Level 10-15 Pokemon and inflict a small amount of damage before throwing another Pokeball.