Test Group WBMXV01.9M44
General Description - Evaporative system monitoring permits detection of leaks in evaporative emission control system with a diameter of .039" (1 mm) and greater. Evaporative emission control system is hermetically sealed off from atmosphere by means of a shut-off valve at charcoal canister. When purge valve opens, engine generates a vacuum in the tank. After closing purge valve, pressure increase is measured by a tank pressure sensor. If vacuum increases above a defined threshold, a leak is detected. As part of the vacuum, check purge flow is verified.
Monitoring Structure - Following conditions must be fulfilled to start monitoring procedure: no malfunction in detecting battery voltage, in detecting vehicle speed, in detecting air mass meter, in detecting coolant temperature, in detecting purge valve signal, in detecting throttle valve position sensor, in detecting idle speed control valve, in detecting shut off valve signal, misfire detection, tank pressure sensor, and secondary air system. See Fig 1-Fig 5 .