1996 Toyota Camry ENGINE ALARM LIGHT ON

Engine Performance problem
1996 Toyota Camry 4 cyl Front Wheel Drive Automatic 180KKM miles

My old faithful Camry 96 - 2.2 GX has been serving me well over the years. Off late I realised that the orange engine alarm light came on and off for few seconds(sometime a minute). It will dissappear for a week before it come back again. There is no noticeable lack of performamnce, however I noticed that the engine idling rpm is a bit unstable, at about 800rpm it will dip to 700rpm and goes back(in split second). I am getting worried if this is a sign of car breaking down or is there a big problem and I need to get it fixed. In this part of the country, I do not know if there is a engine scan available. Otherwise how could we know the cause of such a warning. TQ.

Vince
Malaysia