Your "check engine" light can come on for a variety of reasons, from a loose gas cap to a serious engine malfunction. To determine the difference, you can check your vehicle's error messages by accessing your on-board diagnostics. In 1995, Cadillac switched from the OBD-I diagnostic system to the OBD-II system, and which type your vehicle has depends on when during the year it was made. Neither system is difficult to access.
Turn the ignition key to the "On" position. It does not matter if you start the car or not.
Push and hold the "Off" and "Warmer" buttons on the climate-control panel until the segment check appears on the instrument panel. After the segment check is completed, the instrument panel will display any stored diagnostic codes.
Determine the cause of any codes listed (see Resources).
Exit diagnostic mode by pushing either the "Auto" or "Defog" button, or by turning the ignition off.
Turn the ignition on. You can start the vehicle or leave it off.
If your instrument panel has a digital display, press and hold the "Off" and "Warmer" buttons until the entire display is lit. If your vehicle has an analog instrument panel, simultaneously press the "Off" and "Pass Warmer" buttons on the climate-control panel.
Compare any codes in the system to the manufacturer's list of code meanings (see Resources).
Exit diagnostic mode by pressing the "Econ" or "Defog" button, or by turning the ignition off.
