The Check Engine Light will come on if there's a problem with the Vig's engine management system (PGM-FI). It's usually a sensor. If the D4 light comes on, it usually means the Transmission Control Module has detected a problem, but some PGM-FI problems can cause both lights to come on.

Next time one or both lights come(s) on, you'll have to jump the pins on the Service Check connector (on the passenger side, under the dash or under the carpet by the console). When you do this, either the Check Engine Light or the D4 light will blink a code that will point you to the problem area.

Since yours is intermittant, it sounds like something is "getting ready" to go. If you remove the Backup Fuse (#39 under the hood) it'll re-set the codes. But make sure you know your stereo's anti-theft code before you pull that fuse!

Hope this helps.