1999 Ford Mustang Owner Guide 1st Printing - Page 8

Instrumentation Service engine soon Your vehicle is equipped SERVICE ENGINE with a computer that SOON monitors the engine's emission control system. This system is commonly known as the On Board Diagnostics System (OBD II). The OBD II system protects the environment by ensuring that your vehicle continues to meet government emission standards. The OBD II system also assists the service technician in properly servicing your vehicle. The Service Engine Soon indicator light illuminates when the ignition is first turned to the ON position to check the bulb. If it comes on after the engine is started, one of the engine's emission control systems may be malfunctioning. The light may illuminate without a driveability concern being noted. The vehicle will usually be drivable and will not require towing. What you should do if the Service Engine Soon light illuminates Light turns on solid: This means that the OBD II system has detected a malfunction. Temporary malfunctions may cause your Service Engine Soon light to illuminate. Examples are: 1. The vehicle has run out of fuel. (The engine may misfire or run poorly.) 2. Poor fuel quality or water in the fuel. 3. The fuel cap may not have been properly installed and securely tightened. These temporary malfunctions can be corrected by filling the fuel tank with good quality fuel and/or properly installing and securely tightening the gas cap. After three driving cycles without these or any other temporary malfunctions present, the Service Engine Soon light should turn off. (A driving cycle 8