One problem related to crankshaft position sensor has been reported for the 2009 Chevrolet Cobalt. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2009 Chevrolet Cobalt based on all problems reported for the 2009 Cobalt.
Driving vehicle on highway when engine check light comes on and "reduced engine power" message appears on status bar of dashboard. Repaired at dealership by replacing throttle control body. Occurred twice more over next 3 days, repaired at different dealership saying first throttle control body was defective. Occurred again 2 days later, dealership replaced crankshaft position sensor. Occurred again 1 day later. Need to take in for more service. Basic internet research shows that this is common problem on Chevrolet Cobalts.