Lichtenstein said he plans to review investment in the Carmel insurer by his Steel Partners II fund and start discussions with Conseco managers and directors "concerning the business, operations and future plans."
According to the filing, Steel Partners II owns more than 11 million shares, or nearly 6 percent, of Conseco's outstanding stock.
Steel Partners might seek a board seat and propose different ownership structures, the filing said.
Lichtenstein took over GenCorp Inc., a maker of rocket motors, in 2004. He also forced aside management at United Industrial Corp. and became chairman.
The Carmel insurer lost $65 million in the second quarter largely due to its unprofitable long-term care business. Standard & Poor's and A.M. Best have downgraded Conseco debt.
Conseco stock traded at $14.21 this morning, up a dime. The shares were worth $21 in July.