1998 GMC Suburban Owner's Manual - Page 155

If the Light Is Flashing NOTICE: If you keep driving your vehicle with this light on, after awhile, 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. This light should come on, as a check t o show you it is working, when the ignition is on and the engine is not running. I f the light doesn't come on, have it repaired. This light w i l l also come on during a malfunction in one of two ways: e Light Flashing -- A misfire condition has bee,n detected. A misfire increases vehicle emissions and The following may prevent more serious damage to your vehicle: Reducing vehicle speed. Avoiding hard accelerations. Avoiding steep uphill grades. 0 I f you are towing a trailer, reduce the amount of cargo being hauled as soon as it is possible. I f the light stops flashing and remains on steady, see "If the Light Is On Steady" following. If the light continues to flash, when it is safe to do so, stop tlzc \-,c.l~icle. a safe place to park your vehicle. Find Turn the key off, wait at least 10 seconds and restart the engine. I f the light remains on steady, see "lf the Light Is On Steady" following. If the light is still +lashing, follow the previous steps, and drive the vehicle to your dealer or qualified service center for service. may damage the emission control system on your vehicle. Dealer or qualified service center diagnosis and service m a y be required. e Light On Steady -- An emission control system malfimction has been detected on y o ~ vehicle. ~r Dealer or qualified service center diagnosis and service may be required. 2-77