Service Engine Soon warning light

[hot_sd]

I’m posting this on behalf of a friend who has a 2001 Cavalier. He called me yesterday to say that his check engine light had come on. He does not have a code reader so he asked me to stop by and scan the code for him. Well I did and to my surprise there were no codes.

We then looked at the owner’s manual and it seems there are 2 different warning lights – one is the check engine light which is connected with the engine computer and OBD2 codes – but there is another light called “Service Engine Soon”. This was the warning that had come on. Other than saying that the light indicates a problem and should be taken into the dealership for service there is no real info about this indicator.

The car appears to be running okay.

Can anyone shed light on what this indicator is for.