1998 GMC Savana Van Owner's Manual - Page 130

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