Long story short -

Bought a S2000 a few months ago, with a cluster that had CEL bulb blown. Technically speaking, the CEL has been on since the day I bought the car. Came home and fixed a couple issues that I read with my OBD scan tool. Issues were: knock sensor replacement, missing cat converter, and new secondary o2 sensor. Now that everything is fixed, I erased the codes. Surprised and frustrated, the CEL is still on but no longer finds any codes. Drove it around locally for 5 minutes, turned car off. Drove it at highway speed for 5 minutes, turned car off. The CEL remains. Any thoughts on this? I've read a post that stated it may be a bad ECU but I've never encountered one before so I need confirmation.

Thanks for your help!