We had a 2005 Chevrolet Cobalt towed in the other day because it would not start and, in fact, had to be jump started several times leading up to that point. We charged the battery but quickly determined the battery was bad and needed to be replaced.
After replacing the battery the car started and ran fine but on a test drive we noted the check engine light was on and the car was stuck in second gear, basically a "limp in mode." A conversation with the customer indicated no previous problems like this had occurred.
A computer diagnostic pointed to a communication problem with the transmission control module, and possibly a bad module. Since there had been no previous problems with this car, it seemed something just wasn't adding up. We started an online investigation into possible known problems with this system and discovered a fair amount of hits where the transmission control module needed to be replaced after charging the battery or multiple jump starts.
Now we were on the trail, and found an obscure Internet post about the module losing its ground connection after multiple jump starts. The remedy was to run a new ground connection to the transmission control module. The control module was fairly accessible so it made this correction an inexpensive repair.
The ground connection was made and, just like that, we had communication between the computers. The check engine light went out and the transmission shifted perfectly. In many cases spending some time at the computer researching can save a lot of time, money and frustration.