2002 Saturn L200 service engine and air bag lights stay ill

2002 SATURN L200
82,500 MILES • 4 CYL • FWD • AUTOMATIC
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MADCOMIC2000
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My car has this quirk that when the temperature falls below 40 degrees and the engine is cold that the sevice engine light and the air bag light will stay illuminated after the car is started. When started all lights flash like normal, then go off and those 2 come back on and stay on. Once the engine warms up, if I turn the car off and re-start, then they will stay off for good.

Took it to the Saturn dealer, they scanned with both the lights on and off -- no codes appeared. The scanner can't find anything nor does the computer register a problem. They suggested replacing the wiring harness in the engine compartment. That didn't solve the problem - not a wiring issue.

Does anyone have any other suggestions as to where to check next? Could this be a sensor? Could it be a result of an old battery - 7 years?? Both the mechanic and I are stumped at this point.
Oct 24, 2008 at 9:40 AM
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RACEFAN966
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Ok I think you might have a computer problem but first lets check the temp sensor. Has the temp sensor been replaced yet? The temp sensor (not sender) tells the computer what temp the engine is at and if it is reading incorrectly it can cause some strange problems and not set a code either.
Oct 24, 2008 at 10:37 AM
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MADCOMIC2000
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Wouldn't that show up on the scanner when the tech scans the computer? I thought most sensors will give off a code.

If that is the problem, what kind of $$ are we talking (parts/labor) to fix it?
Oct 24, 2008 at 2:30 PM
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RACEFAN966
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As I have already said no not alway's. The computer reads the sensor if the sensor is giving a reading at all the computer has no reason to set a code it is seeing a reading not anything wrong. Do you have an ohm meter? If so find the temp sensor it should be near the thermostat and look like this


https://www.2carpros.com/forum/automotive_pictures/249564_266445_1.jpg

. Tell me when cold what the ohm reading is across the terminals. You need to unplug the sensor and give the reading of the sensor. No need to start the car or have it running at all ok. This sensor should not cost more then about 25 dollars and you can change it yourself.
Oct 25, 2008 at 8:42 AM
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MADCOMIC2000
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I don't know if this makes a difference in your assessment, but I gave you the wrong light that pops up. Apparently my Saturn has a service wrench light plus a check engine light. The service wrench light and the air bag light are what's popping up.
Oct 27, 2008 at 9:16 AM
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RACEFAN966
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The running problem may still be the temp sensor. As for the air bag light if that can't be scanned by a local parts store for the code then you will need to find a shop for that. Let me know what happens.
Oct 27, 2008 at 11:46 AM