Wireless sensor networks offer various novel applications. Sensor nodes are the simplest devices in the Wireless sensor network but have an important place in meeting environmental challenges when incorporated with applications in multiple fields.Wireless sensor are networks of smart nodes that sense and also have potential to control the resources if programmed so. Reliability for sensor node applications plays a major role in a wireless sensor network. Our experiment based on a malicious sensor node for finding the effect on the technical efficiency of the node processor having auto correlation problem formed by altering the code of the application for the node. Result confirms that an alteration in the code of the application for the node severely affects the technical efficiency of the node processor.