325 oil light

I have a 2002 325i with 120,000 miles. For a while now, the yellow oil light will come on just after I start the car. It goes out after a couple of seconds. It doesn't happen every time. It never goes on after
I've been driving; it's only sometimes after I have started it. The oil level is ok. My regular maintenance non-BMW mechanic says it is perhaps just a sensor malfunction. Does anyone have any experience with this problem? I'm reluctant to take it to the dealer for a $1,000 computer fix ream-job bill! thanks, David Newton
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It is a problem with the oil level sending unit, which lives on the very bottom of the motor, and is easy to replace. You can buy the sesnor on eBay, and your mechanic should have absolutely no trouble installing it on the next oil change.
I have an '00 323 with the same problem -- the oil light comes on about 30-ish seconds after the engine is started, and remains on for 30-ish seconds and goes out, then never comes on again. The oil level is excellent.
I think this is one of those over-engineered circuits, and you can ignore the false signal.

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On Fri, 28 Dec 2007 10:48:00 -0800, David Newton

More than likely the sensor is burned out. Replacing it is a fairly simple affair and you can time it to coincide with an oil change. Just make sure to check the oil regularly with the dipstick until you get the sensor repaired. (And be glad you have an E46 rather than an E90/E92, which has no dipstick and relies solely on the electronic oil level sensor.)
The sensor is about a $100 part. If you have the sedan or the wagon it's dead easy. The sensor bolts into the bottom of the sump and you can drain the oil and then undo the three nuts that hold it on and unclip the wire and replace the sensor. Make sure you use a new gasket. If you can change your own oil, you can replace the sensor on a sedan or a wagon.
With a coupe (like mine) or a convertible it gets more complicated because there's a big honkin' body reinforcement plate in the way. The reinforcement plate comes off with 8 bolts. Be aware that you'll need a fairly long breaker bar or an impact gun to undo the bolts on the reinforcement plate; they're on there pretty good. Use new bolts when you replace the reinforcement plate, and follow the procedure in the shop manual carefully. The bolts are to be tightened in three stages IIRC; don't have the shop manual in front of me at the moment.
One frequent cause of the sensor burning out is leaving the ignition key turned on while draining the oil. Sometimes people get in the bad habit of turning the key on while working on a car so they can listen to the car radio. In the case of the E46 BMW having the sensor completely dry for an extended period will burn out the sensor. Don't do that. Unfortunately many professional technicians (although I would *hope* not the dealership mechanics!) are in this bad habit as well.
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