Sierra 18-9910 Oxygen Sensor Tester & SimulatorUse Sierra 18-9910 Oxygen Sensor Tester and Simulator for testing & diagnostics on any Oxygen Sensor to determine whether the sensor needs replaced.Features: Oxygen sensor signal output is shown in real time on an LED bar graph; Two digit alphanumeric display shows the sensor output cross count per second; Simulates the sensors rich or lean outputs; Automatic detection of common wire misconnections; Compatible with zirconium, titanium and air/fuel ratio sensors; Includes hard shell carrying case;