Malfunction indicator light on - 2003 Jeep Grand Cherokee

when you turn on your ignition to the point before engaging the starter all your warning lights should light up. The Engine Check Light is very obvious, except they throw convention to the wind and show it as 'Service Engine Soon' lamp 'Malfunction indicator lamp (MIL)'.
Page 63 - Section 2-7 Instruments and controls

Malfunction indicator lamp (MIL) If this indicator lamp comes on steady or blinks while the engine is running, it may indicate a potential emission control malfunction. The malfunction indicator lamp may also come on steady if the fuel filler cap is loose or missing, or if the vehicle runs out of fuel. Check to make sure the fuel filler cap is installed and closed tightly, and that the vehicle has at least three gallons of fuel in the fuel tank. After a few driving trips, the lamp should turn off if no other potential emission control system malfunction exists.

http://www.vadennissanservicecontracts.com/owners-manual/nissan/2001-Nissan-Frontier.pdf

..

go have the vehicle scanned for trouble codes most auto stores offer this service for free the codes will help in assisting repair

2014 dodge caravan dash tail light indicator stays on. Is there a problem

Check for codes

Read your owners manual

Why would a Malfunction Lamp come on,
& then go off, if you don't diagnose the problem
& make the required repair.

That technology is 30 years old & your not
up to speed?

The first thing I usually do when seeing a malfunction indicator light on, is to have it scanned with an OBD-II scanner available from Sears, Walmart, or a local auto parts store such as Autozone or Advance Auto Parts. Some auto parts stores will scan it for free.

you can find that out by simply having the fault codes read

usually a sensor has gone bad. have it check by a mechanic on the computer.

When you say malfunction indicator , do you mean `check engine`` light.
These paired lights can indicate a change in engine air flow and fuel mixture. Try a fresh tank of premium fuel, but first a unscrew and re-screw the gas cap until it ratchets into place. The lights can be triggered by a loose gas cap, a fouled O2 sensor, and several other emission related problems including sticking throttle body components, etc.
This can sometimes be sprayed with carb cleaner inserted in the snorkle area of the air intake where teh snorkle meets the metal intake.