CEL came back

The Check Engine Light (CEL) means that an Electronic Control Unit (ECU) found that a parameter is out of bounds by a very significant margin,

The ECU that reads the parameter, has sent a request to the Engine Control Module (ECM) to illuminate the Check Engine Light (CEL).

Using the On-Board Diagnostics port (OBD2) and a compatible Scan Tool, you can retentive Diagnostic Trouble Codes (DTCs),

And then, using those Trouble Codes, we will be able to try and pin point your issue.

I just don't know how serious the problem (...) is

Saying "the engine signal light on" does not give us the required information to tell you the nature of the issue,

We need to know the Diagnostic Trouble Codes to know the severity of the issue.

To get the codes, either purchase a simple OBD2 scan tool, or go to a parts store that offers free OBD2 scans.

Then post the trouble code on the forum, and consider tagging specific people you may want to see your update on the topic using the @ feature.

Also if possible post what was the repair performed previously, what parts and their manufacturer (OEM/ DENSO / Non-OEM)

What was the problem, what codes are coming up, what was the fix, how much did it cost you to fix, does the fix come with a warranty?