Oxygen Sensor Tester

The Oxygen sensor measures the amount of oxygen in the exhaust gasses and it sends signals to the ECU so that it can monitor if the engine is running rich, lean or at stoicheometry. When the tester is connected to the oxy sensor it displays what the air fuel mixture ratio is that the engine is running on. It will display a red light if it is running rich, a yellow light if it is stoich and a green light if it is running lean. The oxy sensor is back probed and connected to the oxy sensor tester. The tester measure the voltage and it displays whit the fuel mixture is.