1998 Chevrolet Express Van Owner's Manual - Page 129

Malfunction Indicator Lamp (Service Engine Soon Light) (Gasoline Engine) NOTICE: If you keep driving your vehicle with this light on, after a while, your emission controls not may work as well, your fuel economy may not as be good and your engine may not run as smoothly. to This could lead costly repairs that may not be covered by your warranty. This light should come on, as a check to show youit is working, when the ignition is on and the engine is not running. If the light doesn'tcome on, have it repaired. This light will also come on during a malfunction inone of two ways: 0 8 1 Your vehicle is equipped SERVICE ENGINE SOON with a computer which monitors operation of the fuel, ignition and emission control systems. I This system is called OBD I1 (On-Board Diagnostics-Second Generation) and is intended to assure that emissions are at acceptable levels for the life of the vehicle, helping to produce a cleaner environment. The SERVICE ENGINE SOON light comes on to indicate that there is a problem andservice is required. Malfunctions often will be indicated by the system before any problem is apparent. This may prevent more serious damage to your vehicle. This system is also designed to assist your service technician in correctlydiagnosing any malfunction. 0 Light Flashing-- A misfire condition has been detected. A misfire increases vehicle emissions and may damage the emission control system on your vehicle. GM or qualified service center diagnosis and service may be required. Light On Steady-- An emission controlsystem malfunction has been detected your vehicle. GM on or qualified service center diagnosis and service may be required. 2-58