The engine computer controls the check engine light.
A flashing check engine light normally means you have a misfire.
A scan tool is required to clear the check engine light. If the failure is not repaired, the light will return.
That's the ubiquitous 'check engine' light.
what is this code p1491 on 2003 jeep liberty
There are pages and pages of things that can cause a check engine light. You need to have it checked with a scantool. Then the code can be diagnosed and repaired.
With an OBD2 scan tool.
Scan tool, will give you a trouble code as to why the computer turned the check engine light on.
The check engine light is reset with a scan tool after repairing the failure that caused the code.
You use a scan tool to check for codes. Then you know what to test.
You reset it with an OBD2 scan tool after it is repaired.
Check your gas cap.