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Dumb question about "Check Engine" light.

Last weekend I cleaned the throttle body on my '95 850 wagon (a.k.a. estate car). In doing so, I disconnected then reconnected a few items that were in the way (e.g. air temp sensor cable). After restarting the engine the "Check Engine" light came on and stayed on whenever the ignition was on. I rechecked the things I had disturbed. The car seemed to run fine so I made a mental note to call the mechanic when I got home from vacation. Today and a few hundred miles later the light went out on its own.

Question: Is it normal for the "Check Engine" light to come on and go off some days later if you disconnect and reconnect some engine sensors? Any thing about this that should concern me further?

Reply to
Donald Newcomb
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Not so dumb... and the answer is "yes" to the first question and "no" to the second. The ECU has learned a lot about how your engine expects to run and will complain with a "check engine" light over things more trivial than the disconnection of sensors. Eventually it gets tired of whining - that is, it learns how to operate the engine again - and turns off the light. The interval is typically specified as a certain number of warm-up intervals, but may include specs for number of times the engine is started and the number of minutes elapsed.

I had to have my '93 Chevy work truck tuned up in a distant town, and it lit the "check engine" light the rest of the day.

Mike

Reply to
Michael Pardee

One of the sensors was not initially reconnected properly. When you double checked everything you must have reseated the connector. In this case, the computer will turn off the light after 3 complete system checks, each of which takes about 30 minutes of mixed driving. If you're really curious about what the problem was, the code will be still stored in the computer for quite a while before it's automatically erased. If you're not curious, or it's inconvenient to get the code read, then you can safely ignore this.

Reply to
Mike F

Thanks to the Mikes for the quick answers.

Reply to
Donald Newcomb

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