1999 Chevrolet Express Van Owner's Manual - Page 125

yellowblue Malfunction Indicator Lamp (Service Engine Soon Light) (4.3L, 5.0L & 5.7L Engines and 7.4L California Gasoline Engine) This system is called OBD II (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 and service 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 correctly diagnosing any malfunction. United States Canada NOTICE: If you keep driving your vehicle with this light on, after a while, your emission controls may not work as well, your fuel economy may not be as good and your engine may not run as smoothly. This could lead to costly repairs that may not be covered by your warranty. Your vehicle is equipped with a computer which monitors operation of the fuel, ignition and emission control systems. 2-57