Continuing west through the southern portions of Bexar County, the loop intersects FM 1937 (South Flores Road) and FM 3499 before an interchange with US 281. The highway continues to the west to an interchange with SH 16, passing to the south of the Toyota Motor Manufacturing Texas plant. The highway continues to the west and begins to curve towards the north as it enters the city limits of Somerset and an intersection with FM 2790 (Somerset Road). Completing the turn to the north as it leaves Somerset, Loop 1604 heads north to an interchange with I-35. The highway heads north after the I-35 interchange to an intersection with FM 2536 (Old Pearsall Road) before an interchange with US 90.