The EVAP monitor usually takes longer to complete than a couple of miles. If the SES light is coming on that soon, I would suspect a "hard fault", in other words, a problem the PCM is "seeing" before it completes the monitor. The EVAP system includes the canister purge solenoid which is in the intake manifold, a vent solenoid near the purge canister, the tank pressure sensor on the top of the fuel tank, and of course the wiring to connect it all to the PCM. It is more than likely one of those items as the monitor needs to run before the PCM can determine a problem with the systems ability to hold pressure.