2005 Buick Rendezvous Owner's Manual - Page 186

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 you experience one or more of these conditions, change the fuel brand you use. It will require at least one full tank of the proper fuel to turn the light off. If none of the above steps have made the light turn off, your dealer can check the vehicle. Your dealer has the proper test equipment and diagnostic tools to fix any mechanical or electrical problems that may have developed. 3-48