Argentina's defence Ministry said seven failed "satellite calls" were picked up in a hopeful sign the crew of 44 was trying to re-establish contact.
The calls lasted between four and 36 seconds in the late morning and early afternoon on Saturday, the ministry said.
The ministry said it was working on tracing the location with an unnamed US company specialised in satellite communications.
Submarines which are stricken underwater can float a location beacon, known as an EPIRB, to the surface that can then emit emergency signals via satellite.
Whipping winds and more than 20ft waves in the South Atlantic have hindered international search efforts for the vessel.