probaly because there is something wrong. If you don't have one already, get a Haynes or Chitlens Repair manual. They break down how to fix just about anything on the specified car. This will tell you how to check the ECM, or car computer. You will watch as the system gives you a set of blinking lights that are coded. You then take the number of long and short blinks ie. 4 long and 3 short, and go to the codes in the repair manual. It will tell you what engine part is sending a problem to the ECM, seeing as there are hundreds of different components that can go bad. Hope that helps. I had the same thing happen and I added more water to water reserve and light went out. the water was about one an a half inches below fill line on tank.
The check engine light on a 2005 Jeep Grand Cherokee looks like this... Here is a link Check Engine Light It looks like a little yellow engine.
With a scan tool.
That is the check engine light.
A flashing check engine light normally means you have a misfire.
Check engine codes, check for spark, check for compression, check fuel pressure, etc.
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.
Disconnect the negative battery cable for about two minutes and that should reset your check engine light.
RADIATOR FAN CONTROL RELAY CIRCUIT
The check engine light stays on when the engine computer has detected a malfunction and set a trouble code.
Misfire? Due for a tune up? Check engine light on?
go to advance and let them shut it off
May want to check flexplate, could be cracked.