The applications of wireless sensor networks (WSNs) have been increased due to its vast potential to connect the physical world to the virtual world. Also, an advance in microelectronic fabrication technology reduces the cost of manufacturing portable wireless sensor nodes. It becomes a trend to deploy the large numbers of portable wireless sensors in WSNs to increase the quality of service (QoS). The QoS of such WSNs is mainly affected by the failure of sensor nodes. Probability of sensor node failure increases with increase in number of sensors. In order to maintain the better QoS under failure conditions, identifying and detaching such faults are essential. Faulty sensor node is detected by measuring the round trip delay (RTD) time of discrete round trip paths and comparing them with threshold value. Initially, the suggested method is experimented on WSNs with six sensor nodes designed using microcontroller and ZigBee. Scalability of proposed method is verified by simulating the WSNs with large numbers of sensor nodes in NS2. The RTD time results derived in hardware and software implementations are almost equal, justifying the real time applicability of the investigated method.