I think that the only way that you'll know for sure what your problem is, is to take it to someone who can scan the ECM for fault codes. The rev limiter will engage under three circumstances. First, overspeed, of course. But it will also activate in response to low oil pressure, and with an overheat condition. In the instance of overspeed, the rev limiter light will illuminate, and it will reduce RPMs to approx 3000 RPM and there is no audible alarm sounded. In the other two instances, it will light the rev limiter light and be accompanied by the other light (oil pressure or overheat) plus an audible alarm. In the case of low oil pressure, it will reduce RPM to approx 1000; for overheat, it will reduce RPM to approx 3000. If it's just an overspeed condition, it should auto reset once you manually reduce throttle to <=3000 RPM for one second or more. It will not reset under the other conditions as long as that condition remains uncorrected. It might be caused by a faulty sensor (hopefully), either oil pressure sensor, or water temp or exhaust temp sensors. I'd check for faulty sensors first, but do try and get it scanned. Hopefully, your indication that it does not affect engine operation is a sign that's it's really just a glitch somewhere, and not indicative of a real problem.
