it is a 90 dakota with a 4 cyl engine,is it obd1 or obd2 or obd1.5 the maintance required light is on and i need to know what that means,also the light that tells me my winsheild washer fluid is low ever though it is full.and the truck sounds like a diesel when it goes down the road even though it has plenty of oil and pressure

 

Should be OBD1. OBD2 did not phase in till 1996. Sensor in the fluid reservoir is probably bad resulting in the light being on all the time.

 

The maintenance required light is for a reminder to check emissions, there is write up on how to reset it in the FAQ in this section (a few posts above this one).
1990 will be OBD1, the maintenance light is separate from the OBD1 computer. Yes, the windshield washer fluid sensor must be faulty or shorted wires.