Hi Renan,
if I remember right there is an additional parameter created with the Adapter Service Template to specify a timeout value.
Additionally check the timeout settings in the SAP Adapters Connection definitions.
Remember to set MinPoolSize to 0 when using Connection Pooling.
Idle Timeout should only apply to currently unused sessions.
But in your case it looks that the active JCo connection gets closed by SAP system before the call is complete.
Might be worth to crosscheck with SAP Basis Team if they can configure something on their side to avoid that the connection gets closed to early.
Regards,
Holger