1998 GMC Safari Owner's Manual - Page 146

Malfunction Indicator Lamp (Service Engine Soon Light) 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 be as good and your engine may not runsmoothly. as to This could lead costly repairs that may not be covered by your warranty. This light should come as a checkto show you it is on, working, when the ignition is and the engine is not on running. If the light doesn't come on, haverepaired. it This light will also come during a malfunction in on one of two ways: SERVICE ENGINE SOON Your vehicle is equipped with a computer which monitors operationof the fuel, ignition and emission control systems. This system is called OBD (On-Board I1 Diagnostics-Second Generation) and is intended to assure that emissions at acceptable levelsfor the life are of the vehicle, helping to produce a cleaner environment. TheSERVICE ENGINE SOON light comes on to indicate that there a problem and service is is required. Malfunctions often will be indicated by the system before any problem apparent. This may is prevent more serious damage to your vehicle. This system is also designed assist your service technician to 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 your on vehicle. Dealer or qualified service center diagnosis and service may be required. Light On Steady -- An emission control system malfunction has been detected on your vehicle. Dealer or qualified service center diagnosis and service may be reauired. 2-62