I remember talking about this one before. Was it yours?
In the 93, the code for the cruise vent solenoid circuit means that your servo is not doing what the PCM is commanding it to do, with respect to venting the vacuum out of the servo.
Make sure you are not reading an old code, too.
According to the 93 service manual, there are four solutions... Replace the computer, the servo, the servo isn't grounded properly (black/white wire), or the dark blue/white wire from the servo is shorted to ground, voltage, or open.
Since it is potentially electrical, you probably need a service manual and a good diagnostic.
1999 540iA Sport
Former 93 SSEi Owner
Former 89 SE Owner