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post #2 of (permalink) Old 02-17-2019
1999 White C5 Coupe
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On my 1999 Corvette, if the check gauge message and light illuminated, a chime would sound. It meant for the driver to check all the guages to determine if one was out-of-range, indicating a problem (such as low oil pressure, overheat, low tire pressure, etc.).

Do all of your gauges work properly? Are any reading inaccurately? I know you stated they were good.

I would suspect a defective oil pressure sending unit (switch) first, or a defective temperature sending unit second. Once a defective switch triggers a warning, however brief, it will turn on the check gauges light (and/or message and chime on some GM cars).

Generally, a defective oil pressure switch will show a drop in oil pressure when the engine oil gets hot at idle. Does the oil pressure light flicker at all during idle?

You can have hot HVAC output, but have a defective engine coolant temperature switch, which tells the computer that the vehicle is not warmed up fully (or is slow to warm up). Generally, that will set a code (with no check engine light) for slow engine warmup, usually meaning the thermostat is stuck open.

I would try the oil pressure switch and see if that corrects the problem. Since raising the idle speed (and raising the oil pressure) causes the check gauge light to go out, Id bet from afar that is your problem. The switch requires a special oil sending unit socket, and do NOT put addtional sealer on the threads (other than what comes on it). I would buy an ACDelco part, and not aftermarket. The OEM switch is inexpensive.

One other thought - if you use a cheap, aftermarket oil filter - that can cause low oil pressure at idle. I would use an ACDelco oil filter also.

Let us know what you determine.
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