1997 Chevrolet Astro Owner's Manual - Page 139

Malfunction Indicator Lamp (Service Engine Soon Light) Your vehicle is equipped with a computer which monitors operation of the fuel, ignition and emission NOTICE: SERVICE ENGINE SOON If you keep driving your vehicle with this light on, after a while, your emission controls may no work as well, your fuel economy may not as be good and your engine may not run as smoothly. This could lead to costly repairs that may not be covered by your warranty. 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: 0 This system is called OBD I1 (On-Board Diagnostics-Second Generation) and is intended to assure that emissions areat acceptable levels for life the of the vehicle, helping to produce a cleaner environment. (In Canada, OBD I1 is replaced by Enhanced Diagnostics.) TheSERVICE ENGINE SOON light comes on to indicate that there is a problem and service is required. Malfunctionsoften will be indicated by the system before any problem is apparent. Thismay prevent more serious damage toyour vehicle. This system is also designed to assist your service technician in correctly diagnosingany malfunction. Light Flashing -- A misfire condition has been detected. A misfire increases vehicle emissions and may damage the emission controlsystem on your vehicle. Dealer or qualified service center diagnosis and service is required. Light On Steady -- An emission controlsystem malfunction has been detected on your vehicle. Dealer or qualified service center diagnosis and service may be required. 0 2-65