Check Engine Light : DTC 55

The check engine light came on a while back. I finally got around to reading the ECU trouble codes. The diagnostic trouble code is 55 - no failure (No self Diagnostic Failure indicated) – this means all is OK.
I then cleared the stored codes on the ECU but the light came back on and again got DTC 55.
Anyone experience this before or know what’s wrong? Do I have to take it in and get Nissan to read/scan it??

Oh yeah my car is a 1995…

Any help would be greatly appreciated, I hate seeing that light on…

thanks
Rick

If everything is fine then why is the check engine light still staying on??

Any ideas?

Thanks
Rick