Oil light comes on only when at an idle

I just had the same problem on an 04 Sebring with a 2.7L V6. The oil pressure sensor (switch) was the culprit. Several web references that I checked mention that the original sensors have issues with oil leakage, which eventually causes it to fail. The sensor itself is fairly inexpensive..about $15. It is located on the back side of the engine and is only accessible from under the car. Look for a small heat shield held on by three 15mm bolts. It is just to the driver's side of where the exhaust system goes behind the engine. The oil sensor is located under this shield. You will need a 1 1/4" deep socket to remove it. When installing the new sensor, be sure to use a torque wrench. It needs to be tightened to 14 ft/lb. Using more force than that, and you run the risk of damaging the sensor.

If this doesn't resolve the problem, you may have a problem with the oil pump either being defective or blocked with sludge. As one of the other gurus on here mentioned, this engine does have a known problem with sludge buildup. I hope this helps! Good luck!

If you just had an oil change, check the oil level. Sometimes the filter or oil pan bolt is not completely secured. Check for any leaks.

I just had this problem on my 2001 in the spring. The oil light would come on at idle after the engine was at full temperature for several minutes. I had about 65K. I fretted over sludge build up which seems to be problem with my engine. You can look under the filler cap to check for any sludge buildup. I even tried using a heavy weight oil. About 2 weeks after the oil change, the problem would resurface. Ultimately changing the oil pressure sensor solved to problem.

Low oil pressure is the reason the light is coming on. The oil pump is driven by the engine. So at idle the pump is turning slowly and not keeping up with the amount of oil required. As engine speed increases the pump overcomes the pressure switch and the light turns off.
Now the cause of it? Well, possibilities include internal engine wear which allows the oil to escape too quickly past the bearings, bad oil pump, too thin engine oil, or even a bad pressure switch(not likely, but still possible)