8691 ECU MONITOR - For use with 1986 - 1991 VW Vanagons. Easy installation provides multiple signal monitoring capability while you test or drive. Unit powered by vehivle 12V battery. Allows monitoring coolant temp, intake air temp, air flow meter volume, O2 sensor feedback signal, O2 sensor ground quality, and battery voltage levels via digital voltmeter display. Start/ run (ignition), Throttle position switch, fuel pump ON, and presence of Fuel Injector, Hall Ignition, and Coil Pulse signals are displayed via front panel LEDs.