2004 Ford Taurus Turn signals and engine light

My turn signals stopped shutting off automatically, around that same time my engine light came on. I was over due for an oil change so I got that done and the engine light stayed on, I reset it manually by taking the post off the battery for a few minutes and putting it back on. It shut off the engine light but a few weeks later, the engine light came back on. Nothing "appears" to be wrong with the car. There are no leaks that I detect, not over heating, all fluids are fine. I run it thru the engine test via the button on the console and everything comes back "OK". Please help!