General Technologies Corp GTC ST05 Oxygen Sensor Tester and Simulator The sensor signal output is shown in real time on the bar graph, while a 2 digit alphanumeric display shows the sensor output cross count per second By pressing the Test' button and performing a snap throttle acceleration of the engine, it tests the response time of the sensor and shows a pass or fail result within seconds Two buttons allows for simulation of rich or lean conditions to monitor response of the engine control module Diagnoses "lazy" (slow response) sensors, which may not set DTCs, but cause drivability problems Sensor can be tested on or off the vehicle