2003 GMC Sonoma Owner's Manual - Page 162

This light should come on, as a check to show you it is working, when the ignition is on and the engine is not running. If the light doesn't come on, have it repaired. This light will also come on during a malfunction in one of two ways: e 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 ieast i0 seconds and restart the engine. If the light remains on steady, see "If the Light I On Steady" following. If the light is still s flashing, follow the previous steps, and drive the vehicle to your dealer or qualified service center for service. Light Flashing - A misfire condition has been detected. A misfire increases vehicle emissions and may damage the emission control system on your vehicle. Dealer or qualified service center diagnosis and service may be required. e Light On Steady - An emission control system malfunction has been detected on your vehicle. Dealer or qualified service center diagnosis and service may be required. 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 5-7. 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. If the Light Is Flashing The following may prevent more serious damage to your vehicle: e Reducing vehicle speed. Avoiding hard accelerations. Avoidingsteep uphill grades. If you are towing a trailer, reduce the amount of cargo being hauled as soon as it is possible. e e 3-35