In some cases the MIL light can be turned off by simply resetting it. More then one malfunction indication has been the result of a transient condition that does not recur. On the other hand, a legitimate malfunction may be the basis for an MIL being illuminated. And in still other situations, engine modifications may be the MIL-triggering culprit. If the cause isn’t readily apparent, diagnostic equipment is required to both reset the MIL and determine the reason it was illuminated in the first place.
    Several diagnostic tools are available, but most include hand-held hardware and are fairly expensive. A nice alternative is AutoTap, a program that runs on just about any PC. (The current version runs under DOS, a new Windows version should be released shortly.) Included with the software is a cable that connects a laptop or desktop PC to the vehicle’s PCM (Powertrain Control Module). After it’s connected and communicating with the PCM, AutoTap can be used to display data from all the vehicle sensors or from a specific group that can be individually selected.