2010 GMC Sierra 1500 Crew Cab Owner's Manual - Page 267

This light comes on during a malfunction in one of two ways: Light Flashing: A misfire condition has been detected. A misfire increases vehicle emissions and could damage the emission control system on the vehicle. Diagnosis and service might be required. To prevent more serious damage to the vehicle: ... An emission system malfunction might be corrected by doing the following: . Reduce vehicle speed. Avoid hard accelerations. Avoid steep uphill grades. If towing a trailer, reduce the amount of cargo being hauled as soon as it is possible... Make sure the fuel cap is fully installed. See Filling the Tank on page 6‑12. The diagnostic system can determine if the fuel cap has been left off or improperly installed. A loose or missing fuel cap allows fuel to evaporate into the atmosphere. A few driving trips with the cap properly installed should turn the light off. If the vehicle has been driven through a deep puddle of water, the vehicle's electrical system might be wet. The condition is usually corrected when the electrical system dries out. A few driving trips should turn the light off. Make sure to fuel the vehicle with quality fuel. Poor fuel quality causes the engine not to run as efficiently as designed and can cause: stalling after start-up, stalling when the vehicle is changed into gear, misfiring, hesitation on acceleration, or stumbling on acceleration. These conditions might go away once the engine is warmed up. If one or more of these conditions occurs, change the fuel brand used. It will require at least one full tank of the proper fuel to turn the light off. See Gasoline Octane on page 6‑7. If the light continues to flash, when it is safe to do so, stop the vehicle. Find a safe place to park the vehicle. Turn the vehicle off, wait at least 10 seconds, and restart the engine. If the light is still flashing, follow the previous steps and see your dealer for service as soon as possible. Light On Steady: An emission control system malfunction has been detected on the vehicle. Diagnosis and service might be required. 4-43