I would bet on the pressure sender, but you must not bet your engine on it. My approach is to blindly replace the sender - they are high failure rate devices, fairly cheap, and have a very good chance of correcting the problem.

EDIT - Good that the oil pressure light has gone out. According to the source the throttle body will relearn by itself in three restarts.

Flashing check engine light means you have a misfire that serious enough to damage the catalytic converter. Stop guessing and get the trouble codes read. Asking us which of the possible 3,000 codes is stored in your computer is crazy.

Read this post on flashing check engine light and the second one on using the wrong viscosity oil

http://ricksfreeautorepairadvice.com/che...

first have the codes read by Autozone or equivalent.

http://blog.carmd.com/flashingcheckengin...

The flashing engine light means misfire and can be dangerous for your engine. See the above web site.

Your oil pump could be failing, your oil pressure could be too low.

go to an auto parts store ans have the codes read

I think first you may using the wrong grade of oil it could be 5w20 also change oil sensor do this first.

My check engine light flashes on but it has oil, the oil is new but seems kind of thin; its 10w30 oil and I have a 2004 Chevy Aveo 1.6L Engine. I have just rebuilt the engine and, at the beginning, there was white smoke coming out of the engine, especially around the exhaust manifold where it attaches to the engine. Some white smoke would come out of the oil fill hole in the engine. Gradually, I've been letting the car run and I've driven it around the neighborhood and now it doesn't smoke anymore. Water was coming out of the exhaust pipe as well, but it has now reduced to a couple of drops. I put coolant and oil, but the check oil light is flashing on, but it has enough oil. Do you think I have to reset something, or something else is wrong with the car? I heard that it might be the oil pressure sending sensor.