The Check Engine light can come on very easily I have discovered. Once on, it has to be reset and will not clear itself. There may be something that wasn't hooked up or connected from that Smog Test. My Check Engine light has come on three different times so far. A bit annoying but nice to get the heads up.
The first time was because the electric fan circuit for the radiator cooling was not working properly. The second event was due to a cracked charcoal cannister for the fuel system. The driver seat and floor had to be opened for that fix and the cannister was only available from Germany but all was fixed in a few days. The third event just weeks ago was claimed to have been the gas cap perhaps not screwed on properly or tight enough? I hope that was it. I hate when that light comes on but I am not one of these people that will leave it that way. You never know what could be wrong.
I also had the Selector Lever indicator system go out on me. When I moved the shift lever, the display on the dash remained in D (drive) regardless of the lever position. Because of this the computer did not want to let me start the rig. If you try enough times, it overrides the system and lets you drive to service. This malfunction also disables the Cruise Control feature. Got it all fixed; happy camper!