It is a vacuum test, checking for the system to hold vacuum for a certain amount of time. It requires a number of conditions to met in order to run the test. The WiTech scan tool can run the test under the PCM Small leak verification test.
That is not a pump, it is a charcoal cannister and an Evaporative System Integrity Monitor (ESIM). The ESIM closes to prevent vapor from escaping, and this also allows a vacuum to be created as the temperature drops when the car is parked. Also, the ESIM is closed when the purge solenoid is working to allow vapor from the cannister to be drawn into the engine and burned. The system monitors vacuum or pressure in the fuel tank and cannister using natural vacuum that is created by the temperature change noted above.
When I rebuilt the car this year I had all of the Evap system out from under the wheel well as well as the fuel filler neck. I am thinking I may have pinched an O ring putting it back in or something is not tight enough. I have not had time lately to look at it, hopefully this weekend. I just was curious how the system acutely worked before I started on it.
Well I had time to look at the Evap system in my car tonight and I think I found the problem. I took the canister out to inspect it and found a nice crack around the mounting bracket. I guess I was a little to eager to get the car back together that I did not look at it close enough before I put it back in. We had one from our parts car so I put that one in. I cleared all the codes and hope that takes care of it.