2000 Cavalier Service light when car is put into gear

My 2000 Cavalier was just in for service to have the left and right turn signals fixed (the bulbs must have burned out). A few days later the service light started coming on after I put the car in gear. It doesn't happen when I start the engine or when its idling, just when it's in gear. Once when my husband rode with me in the passenger seat, (of course), the service light didn't come on. And once every so often it won't, but for the majority of my time driving, the service light goes on and stays on.

The "check engine" light is an indicator for a system that monitors many electronic functions in the system, also called the "malfunction indicator lamp" (MIL). It can come on for any of hundreds of different causes from any of the systems that the computer monitors. Some are very important and can lead to further component or engine damage and some are emissions related not as serious but still a problem and need to be repaired.

Your first step is to have the computer scanned to retrieve the trouble codes that were set when the check engine light came on. Those codes will give you specific information about what the computer saw and will get you pointed in the right direction to find your problem. With a 1996 or newer and some 95 cars and you have an AutoZone or Advanced auto parts in your area, they will read them for free. Once you have these code numbers, we can be a lot more specific about what your problem may be.