What does it mean when my 1999 Chevy cavalier engine light comes on for no apparent reason?

Answer 1

This might not be an improvement to the previous answers but take it for what it is. I have the same care and year. The check engine light had been coming on for a couple of days or weeks and then going off..I noticed a lot of things on that car changed because of a temperature rise or fall outside..which seemed dumb to me.( I mean except if there was no coolant)

i went to Advanced Auto and asked them to run codes (they do it free)...the code came back as bad o2 sensor. I left drove home and of course the light was out by then.

I found out that this is a common problem for the car. The check engine light is on. but is the computer checking the check engine light??? Anyway it was time for Emissions and I took it.

.I thought the girl was going to do the test with the thing they put in the tail pipe and what i had experienced before. The check engine light came on when I was in line( note there was no problem I could feel or smell in this car in as long as I driven it knowing the check engine light was a problem)..So the girl does something but nothing with the tailpipe..remember light on ..she is running codes and fails me. I got out of the bay and the light went off..so I figured you know what..I turned around went back through the line and passed 2 minutes later.Take it for what it is..but I think the check engine light needs to check itself.