The Da Nang Boys have taken Mike Toreno and are holding him in a van, and Jizzy sends Carl after it with a signal meter rather than a location. The bar strengthens as the van gets closer, which makes the search the first half of the mission.
Getting him out means destroying the van he is in, then getting him clear before the police arrive, then losing them at a Pay 'n' Spray. Toreno spends most of the game after this pretending to be somebody else, and this is where Carl earns the favour he later cannot refuse.