After Serge Gnabry skilfully put the host in front, Bayer Leverkusen midfielder Kai Havertz swept home Die Mannschaft's second of a game in which Argentina offered very little until substitute Lucas Alario pulled one back in the 66th minute.
Lionel Messi missed the game while he served a suspension but Lionel Scaloni fielded a strong team including Paulo Dybala, Lautaro Martinez and Roberto Pereyra in attack.
Low took the opportunity to give debuts to Gian-Luca Waldschmidt on the wing and Robin Koch in defence and was rewarded with an hour of dominance before a late rally culminated in Ocampos poaching an equaliser that silenced the crowd in Dortmund.
Argentina was undone after 15 minutes when Lukas Klostermann got around Angel Correa and played a low cross towards Gnabry, who nipped in ahead of three Argentina defenders and poked the ball into the far corner of the net from six yards.
Another Klostermann break brought Germany's second goal, the RB Leipzig wing-back pouncing after Marcos Rojo yielded possession and surging forward to feed Gnabry, whose slide-rule pass into the box found Havertz unmarked for an easy finish.
Marcel Halstenberg crashed a stunning 30-yard free-kick onto the underside of the crossbar before Argentina's Rodrigo de Paul hammered a similarly spectacular effort onto the post at the other end but at the interval the hosts deservedly led 2-0.
Emre Can forced Agustin Marchesin into a save on the edge of his penalty area early in the second half before Scaloni sent on Alario for Dybala.
The Bayer Leverkusen striker had been on the pitch just three minutes when fellow substitute Marcos Acuna picked him out with a floated cross from the left and he arrowed a header into the far corner of Marc-Andre ter Stegen's net.
A Joshua Kimmich free-kick tested Marchesin in the closing stages but the Porto goalkeeper punched it clear before Alario's run sliced Germany open and Ocampos side-footed home via a deflection off Can, beating Ter Stegen at his near post to Low's dismay.