what could make my engine light come? on 1995 Plymouth Neon

my check engine llight came on for about a week then turned off for a few more days now its back on again.

Asked by for the 1995 Plymouth Neon
If the Check Engine Light/Service Engine Soon light illuminates while you are driving, the car's on board computer sees a fault in the engines management system that is causing an excess amount of pollutants to be emitted from your car. This could result in engine damage if left neglected. Some problems that can cause the Check Engine light to stay on may take two "drive cycles' to complete before illuminating the Check Engine Light. The computer sees a problem and looks for an identical set of circumstances to occur to confirm that it has indeed seen a problem before turning on the light. A Check Engine light that continually flashes while you are driving is serious and is a sign that the computer sees a problem that seriously risks damaging the catalytic converter which may result in an expensive repair or even may cause a fire! Diagnostic codes are stored in the vehicle's computer and can be retrieved using a scantool that communicates with the computer in your car. We have in our Repairpal website an encyclopedia with in depth articles about computer, and computer control systems, emission and driveability problems.
You need a scan tool to retrieve codes if you got the codes (they will look like P0420,or P1435....)and could post them we may be able to tell you what the likely causes of those codes are.