Check Cooling System light question

[doogie240]

My 96 SE's (KA) check cooling system light has recently come on. My car has been running fine since the light has come on, temperature gauge still reads the same, no strange smells, coolant levels look good, but the car has been backfiring more than usual (Apex'i dual exhaust). No strange smoke either.

Also, before the light came on, my gas mileage has dropped by about 4 mpg. This may also be due to the fact that it has been winter and I have had my winter wheels on the car, but I dunno.

Any suggestions on what I should start checking to get the light to go off?

[g6civcx]

What does a check cooling system light look like?