Oil level sensor issue

[kretzj]

When I start my 94' 740i, the low oil message appears on the computer. After ~50 sec, the message disappears and never reappears unless I restart the car. I know the physical level is fine. If the level sensor was bad, wouldn't the error message stay on? A new sensor is ~$150 and I don't want to waste my money if there is an easier fix.

Jon

[autobonrun]

I doubt the sensor is bad, but rather out of calibration.

I think certain messages that are not immediately critical (like oil or washer fluid level) do clear so as not to tie up your display; unlike something like oil pressure. They typically do not reappear until you turn the car off. I started having a problem with the oil level warning on my 93 when I switched to synthetic oil. Before that I never had a problem. If the level switch is a float type or displacer type, then the density of the oil will cause it to ride at a different point in the fluid for the exact same level. This can be just enough to cause an early warning. On my 93, I was told the switch was internal to the sump and difficult to access. When I check the level, it's about halfway between the two marks when the warning activates. It doesn't take much to clear it. I usually just fill it back to the max line.

See how much oil you need to add (within the recommended maximum) to clear the warning. I just keep my level slightly above the warning point and recognize it's not really low when it goes off. If you fill it to the max line and the warning clears, the sensor is not bad, just out of calibration. But, I don't think there is a calibration adjustment on the switch. The dealer and mechanics I've talked to do not know. Also find out where your sensor is located on your 94. Hopefully its external to the sump.

[Larry F.]

Jon:

I know this is "old news", but anyway: I had the same symptoms with my 540i/6, and the cure was replacing the sensor. Yes, it was a bit spendy, but it can be accessed from under the car without having to disassemble anything. Of course, you need to do it at an oil change, since it is at the bottom of the sump!

Good luck! Larry F.