Saturn Repair: automatic transmission 94 saturn sl1, saturn sl1, auto zone

Question
i am having trouble with my transmission ,it runs great on highway but sometimes when im only doing between 15 to 40 mph it will shift hard or downshift on its own and the engine light will come on ,this doesnt happen all the time but at least half the time im driving it

Answer
First off get the car to normal operating temperature and put it in park and then check the fluid llevel. Have the codes pulled from the computer auto zone will do it for free.  Unfortunately these cars are known for the valvebody going bad. Let me know about the fluid level  and what codes are found.