One problem related to automatic transmission control module has been reported for the 2007 Saturn ION. The most recently reported issues are listed below.
The car made a loud noise when I pressed on the gas. It would not accelerate fast enough for the highway and the speedometer was not working. I'm guessing the car could go at max, 20mph. The speedometer remained on 0 while the acceleration had to go up to 3 or 4 just to keep the car moving. The check engine light was on. I took the car to gm dealership/certified Saturn service right then, and they charged me $360 to replace the transmission control module. The service guy told me that when mechanics first did the electrical diagnostic check, the car failed 32 markers, but when they did an electrical diagnostic check after replacing the transmission control module, the results confirmed that all the car's problems have been fixed.