Corey Ashe assisted on a strike by Cam Weaver in the 49th minute and had an unassisted goal in the 69th minute for the Dynamo.
Eddie Robinson had Houston’s first point of the game in the 12th minute on an unassisted goal.
Orlando Rodriguez was fed a pass by Alejandro Velez in the 69th minute for Arabe Unido’s only goal.
Both teams are tied for second place in the four-team group at 2-1-1 with seven points, two points behind leader Pachuca of Mexico (3-1-0, 9), but should both teams be tied at the end of the six rounds of pool play, Houston would have the tiebreaking advantage, based on goal differential.
Houston will next host Pachuca next Wednesday in Round 5 play.
Arabe, who lost their first game in the tournament, will host Metapan of El Salvador (0-4-0) next Tuesday night.
Metapan has already been eliminated from the event.
