Battery/Alternator/Engine Light

So I recently had to have my battery and alternator replaced because my car died on the side of the road. The mechanic I took it to said they did a diagnostic and determined that this was the problem. I got the car back today and as I was driving home from work the check engine light came on. This was not a problem prior to taking my car in. Is there any reason for this?

There are dozens of possible reasons why the check engine light has come on. It may or may not be related to the alternator failure. The light is an early warning, not a sign of impending doom. It means something is functioning outside its normal range.

I suggest you check all of the fluids and look for something obvious, like a loose belt or disconnected wire somewhere. Then wait a few days. The light may go off after a few start/drive cycles.

If the light stays on you’ll have to have to computer scanned for trouble codes. Most auto parts stores will do this free.

May not be related. Knowing what make model and year of car could be helpful for us.

That CEL (check engine light) is just a kid in class waving her hand trying to get you attention because she has the answer. You need to have the codes read. Some places will read them for FREE. Try Autozone or Advanced Auto Parts. Get the exact code (like P0123) not just their translation into English and post it back here.