2003 Chevrolet Astro Owner's Manual - Page 157

If the Light Is Flashing The following may prevent more serious damage to your vehicle: Reducing vehicle speed. Avoiding hard accelerations. Avoiding steep uphill grades. If you are towing a trailer, reduce the amount of cargo being hauled as soon as it is possible. If the Light Is On Steady You may be able to correct the emission system malfunction by considering the following: Did you recently put fuel into your vehicle? If so, reinstall the fuel cap, making sure to fully install the cap. See Filling Your Tank on page 5-8. The diagnostic system can determine if the fuel cap has been left off or improperly installed. A loose or missing fuel cap will allow fuel to evaporate into the atmosphere. A few driving trips with the cap properly installed should turn the light off. Did you just drive through a deep puddle of water? If so, your electrical system may be wet. The condition will usually be corrected when the electrical system dries out. A few driving trips should turn the light off. Have you recently changed brands of fuel? If so, be sure to fuel your vehicle with quality fuel. See Gasoline Octane on page 5-5.Poor fuel quality will cause your engine not to run as efficiently as designed. You may notice this as stalling after start-up, stalling when you put the vehicle into gear, misfiring, hesitation on acceleration or stumbling on acceleration. (These conditions may go away once the engine is warmed up.) This will be detected by the system and cause the light to turn on. If 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 the vehicle. Find a safe place to park your vehicle. Turn the key off, wait at least 10 seconds and restart the engine. If the light remains on steady, see "If the Light Is On Steady" following. If the light is still flashing, follow the previous steps, and drive the vehicle to your dealer or qualified service center for service. 3-32