check engine light on 1991 Mitsubishi Galant

Why does "the check engine" light come on but no codes come up with a diagnostic check. Light was shut off but came back on within minutes of running. Car has 120,000 mi.

by in Needham, MA on August 14, 2010
2 answers 1 comment
ANSWER by , August 14, 2010
If the idle speed is too low this can happen, does the light go out if you rev the engine up?
COMMENT by , August 16, 2010
No, it just stays on all of the time.
ANSWER by , March 28, 2011
Make sure your gas cap is on tight and makes a good seal. We've experienced this two times and both times it was corrected by tightening the cap better.