One problem related to service engine light on has been reported for the 2003 Saturn ION. The most recently reported issues are listed below.
I have been having some issues with clunking and grinding noises when going over bumps or potholes or while making turns. I took my 2003 Ion 2 to have this checked and I found out that the problems was both of my control arm bushings. My car is 2 months out of warranty and has only 38,000 miles on it, so at first I thought that this could be untrue. But, after internet research it seems that many 2003 Ion drivers have had this problem. I called my Saturn dealer and they acted like they had never heard of this problem and could do nothing to help me or fix it. My other problem with the car, which also seems to be a common problem, is that the service engine soon light comes on intermittently. One day it will be on, and the next it will be fine.