Originally Posted by
97K15004WD
What year is your vehicle? OBDII requires different responses from the monitoring sensors, depending on the year. PCM is looking for .040 size leak in one year, .020 size leak in others, in some, doesn't care. EVAP system holds tank vent gases and if not done properly, can vaccuum your tank flat. Be aware that the solenoids allow engine vac to draw vapors into the engine after an off cycle and a certain outside temp is met. PCM goes into test mode to check for leaks by creating small vac and then times how long it takes to reach atmospheric pressure (uses MAP and pressure sensor in the tank to compare).
Thats why he said "vaccuum leak".....