I have a 19991 toyota previa. the oil level light

If the light is flashing there could be problems with the electrical wiring. The easy places to check are at the bottom of the oil reservoir (pass. side under the hood) and at the driver side of the oil pan under the vehicle where the wires plug into the sensor. If this doesn't resolve the problem then it isn't easy, and testing the circuit will have to be done by someone who knows their electrical "stuff." Even the pump motor for the reservoir could be out.

If the Oil Level Sensor light stays on and you have already checked to make sure the oil level read on the dipstick under the driver side seat engine compartment is reading adequate, then you have a sticking oil level sensor float. Replacing the oil level sensor is easy, but extremely expensive ($485 in 2012). You can try to clean the plastic spool that the float slides on, but the problem is usually that it has swollen or expanded (likely from heat in the oil). One could try to sand it down but this would be difficult. I have made a new part out of nylon 6/6 on my lathe and replaced the plastic spool so far with excellent results. I'm considering selling it as an aftermarket part when I see if mine works. It would be a lot less than $485 dollars from Toyota. Or possibly have people send it to me and I'll repair the sensor myself.

Have u checked the oil's stickiness & color? It could be its telling you to change the engine oil.......sodeep