Check Engine Light

[1997 240SX SE]

Had this 97 SE for about 3 weeks now and it has run beautiful..in fact it still does. Tonight my check engine light came on....Not sure why, engine sounds fine and idles fine...Maybe bad O2 sensor??? Exhaust doesn't smell too bad but maybe bad Cat Converter.....Any suggestions?

[wazneeni]

Whattaya know...I've got the same problem.  Check the codes, get an 0303 (front O2 sensor), reset the ECU, lights pops on 2 days later.  I need to replace the spark plugs, reset the ECU, wait for a code, then replace O2 sensor if I need to.

As for you, check the codes.  Won't know much until then.