Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.1 exptools 1/6/84; site iham1.UUCP Path: utzoo!watmath!clyde!burl!mgnetp!ihnp4!iham1!rls From: rls@iham1.UUCP (Rick Schieve) Newsgroups: net.auto Subject: Re: Idiot light question. Message-ID: <181@iham1.UUCP> Date: Fri, 10-Aug-84 09:31:52 EDT Article-I.D.: iham1.181 Posted: Fri Aug 10 09:31:52 1984 Date-Received: Sat, 11-Aug-84 00:27:32 EDT Organization: AT&T Bell Labs, Naperville, IL Lines: 25 The check engine light on late model GM cars does not really qualify is an idiot light as most people think of them. It does not monitor a specific engine function, but rather it lets the driver know that the computer control thinks something is wrong. The computer has multiple inputs such as engine temp, barometric pressure and even a sensor in the exhaust. It in turn controls gas flow, spark advance, etc... Any time the check engine light comes on while driving, it is an indication that the computer is not happy with something and if it is not happy ist can screw up the car in many ways. The fact that the light came on tells no specifics. THowever, as long as power is not lost to the computer, it remembers what it was complaining about. Its memory can be dumped by shorting two terminals together at the diagnostic jack under your dash. The check engine light will actually flash an error code indicating its specific problem. Buy or borrow a service manual. The specific procedure along with diagnostic flow charts will probably pin point your problem. I was skepticle myself until my wife's 81 Camaro had some problems and after reading the error code the service manual pointed right to the faulty computer temperature sensor (which is not the same as the sensor that runs gauges or idiot lights). Rick Schieve