Sierra 18-9910 Oxygen Sensor Tester Simulator Use 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 airfuel ratio s