When I bought my civic, it didn't have an intake, so I purchased one from ebay and changed the intake sensor that's plugged into the intake. So, the guy I bought it from said that the Check engine light was on because it was missing the intake and even after I installed it, the light is STILL ON.
I've gotten the car scanned, but no codes come up. The scanner says there's nothing wrong with the car.
So what could be the problem?? Should I scan it again??
What should I check or replace??
ps: I've already tried to make the light go away by unplugging the car overnight, but the light still comes on regardless.
THANKS!

 

and you did disconnect the battery from the power and ground

 

Have Autozone or wherever clear the codes, then see if the CEL comes back on. If that doesn't make the CEL go away, we'll have to troubleshoot further.

 

I already tried disconnecting the battery to clear the codes, but the light still comes on.
Auto Zone won't do that here in California.

 

When the light is on, there is a code that can be scanned(unless... see below). The '98 should respond to the OBD1 style scan of connecting the test wire and counting the CEL blinks. This has only a limited set of codes compared to what you can see on OBDII though. If you can't borrow one, it would be better in the long run for you to have your own OBDII scanner.

Also note that if the test jumper is already in place yet there are no codes, the CEL will light up steady to tell you to remove it (the jumper sets the spark timing to a constant value so the distributor can be adjusted). I'm not sure what the OBDII does in that situation.