Secure routing protocols in Mobile ad-hoc networks (MANET) have been extensively studied in recent years. Most Routing Protocol, however, are based on authentication, cryptographic schemes, security association and key distribution and so on. In this paper, we propose an enhanced MANET routing protocol, which prevents security threats, especially by employing route investigation. When an intermediate node that is on a path between source and destination receives two types of control messages (RREP and RERR), the intermediate node sends them to the source in pure AODV. However, in our method, the node which receives the control messages confirms it using Route Investigation Request (IREQ) and Route Investigation Reply (IREP). Through this investigation procedure, we can gain reliability of path for transmitting data packets in MANET. Simulation results show considerable improvement in the packet delivery ratio and the end-to-end latency at the expense of the moderate increase of control message overhead.