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Discussion Starter · #1 ·
Red oil light flickers when to a stop and idling in D afterbeing driven for >10 miles. When in D, the car idles at just above 500 RPM from reading the tach needle, which I believe is considered to be on the low side. In every occurance the light seemed to cleared itself after shutting the car off, but invariably resurface randomly in a later time.

I had this problem for a year now, and I had brought the car the the dealer for diagnosis three times. First time they checked oil pressure, it was OK and we left it at that. Second time they replaced the oil LEVEL sensor along with Inspection II. Third time they replaced the oil pressure switch.

Each time the pressure light flicker has came back...it becomes the worst after they replaced the oil pressure switch, now the light will stay lit when idling in D but will go away once the engine revs up a little. Now the car is scheduled for another dealer visit where they will investigate things further.

It seems this problem is rather common with BMWs (not just E46) after googling a bit, but no definative answer as to the cause. The most common suggested fixes are to replace the pressure switch, change the oil and filter, and replace the oil pump. But after trying two of these suggested fixes the problem remains.

How many of you 'festers out there have this problem? And have you gotten it fixed? Please share your stories....

Thanks
 

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Not normal and not common to my knowledge. How many miles on the car and what oil are you using? You have low idle oil pressure. Causes include (but not limited to) the wrong oil, the oil pump is bad, the intake screen is clogged or you have excessive bearing clearances preventing the buildup of oil pressure at idle.
 

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The number 1 enemy of the oil pressure switch in our cars, moisture! If you aim the pressure washer directly at it, say goodbye to it. If oil leaks out at the connector and through the switch, say goodbye to it. If the yellow oil can is displayed, it's not pressure so hang on to your oil pressure switch. If you have an oil pressure problem, you bet theres sludge and you may need more than an oil pump.
 

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Discussion Starter · #4 · (Edited)
Keith,
The car has 28k on it. All oil changes were done by the dealer so I guess they used BMW's recommended oil (Castrol i think). Since I had the car i changed oil once per calendar year due to my annual miles is about 7k. I travel a lot for my work the car spends most of its time during the week parked outside in the elements, not sure if that has something to do with it.
 

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The first time

I changed my oil, I used the recommended Castrol Oil, or I thought I did. My light was flickering under exactly the same circumstances as yours. It turned out I had not used the European blend, which is LL01 approved. The non-European blend is not. After I changed the oil & filter and started using the European blended Castrol or Mobile-1 I never had the problem again. It could have been a coincidence, but it did pretty much stop immediately after I put in some LL01 approved oil...
 

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Discussion Starter · #6 ·
An update with the dealer's diagnosis:

The shop foreman, along with BMW technical services, offered four possible causes:
1. electrical short in the wiring harness where the wire of the pressure sensor goes through
2. DME (engine management computer) module defective
3. Instrument panel defective
4. "air bubble" in the oil causing pressure switch to trip

The dealer was able to duplicate the problem only once during their test drive, and the pressure was within spec according to them. The fix as of now is to re-wire the sensor to bypass the harness and thus the possible short.
 

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I have the same problem! Oil light flickering red at idle, usually after the engine is warmed. The dealer checked oil pressure and it read 18 hot which is ok. So they replaced the oil pressure switch. That was last week, then yesterday the problem returned. Taking car back into dealer tomorrow.
 

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Discussion Starter · #8 ·
Hey Burrito, I'm still not totally sold on the electrical short theory. When the light starts to flicker, try put the car in neutral and see if your rpm rises and th elight goes away. I tried on mine and the rpm rises to about 700 and the light goes away, drop it back into D and the light comes back on again ... :dunno:
 

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An update with the dealer's diagnosis:

The shop foreman, along with BMW technical services, offered four possible causes:
1. electrical short in the wiring harness where the wire of the pressure sensor goes through
2. DME (engine management computer) module defective
3. Instrument panel defective
4. "air bubble" in the oil causing pressure switch to trip

The dealer was able to duplicate the problem only once during their test drive, and the pressure was within spec according to them. The fix as of now is to re-wire the sensor to bypass the harness and thus the possible short.
I love how they go for wiring harness or DME or other sceniaros when they just can't find the actual problem.
Ask them if they will credit you back on the parts that they replace and it turns out the parts they replaced are NOT the actual cause!..
 

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I have the same problem! Oil light flickering red at idle, usually after the engine is warmed. The dealer checked oil pressure and it read 18 hot which is ok. So they replaced the oil pressure switch. That was last week, then yesterday the problem returned. Taking car back into dealer tomorrow.
Isn't the oil sensor on the bottom of the oil pan pretty well known for crapping out? Could that possibly the problem? :dunno:
 

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Hey Burrito, I'm still not totally sold on the electrical short theory. When the light starts to flicker, try put the car in neutral and see if your rpm rises and th elight goes away. I tried on mine and the rpm rises to about 700 and the light goes away, drop it back into D and the light comes back on again ... :dunno:
Update

The dealer re-analyzed the oil pressure on my car, but this time with the transmission in D. They are saying the oil pressure registered slightly low at idle (but he didn't give me the number which I would be interested in knowing.) They think the problem is with the oil pump but they can't be sure. It would cost $2600 to find out (dropping the oil pan, etc.) Since the flickering light isn't happening very often I am just going to live with it, unless it gets worse.
 

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Well, I have a Bentley manual and some tools. *In Theory* I should be able to diy, but that would be the most complex thing I've ever done in my life. I want to tackle replacing the belts first and see how that goes.
I'd try it. Even if you blow your motor you can still buy a used one for less than $2600! :thumbup:
 

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Oil Pressure Light intermittently flickers in drive

I love how they go for wiring harness or DME or other sceniaros when they just can't find the actual problem.
Ask them if they will credit you back on the parts that they replace and it turns out the parts they replaced are NOT the actual cause!..
I am having a similar experience with my 2003 325i;the light had been flickering for several weeks when engine was hot, at an idle, in drive. I replaced the oil switch-same problem, checked oil pressure at an idle in "drive" when hot, pressure = 9 lbs (factory min.spec. is .5bar= 7.5 lbs); brought car to the BMW dealer who measured 15 lbs and suggested that the problem may have been due to a low battery( alternator had failed one hour earlier) and there was no oil pressure problem; the dealer replaced alternator and battery. One day later after 20 minutes of driving, the light began to flicker once again. It appears that: 1. The BMW dealer failed to reproduce the problem in that the conditions as reported were not duplicated, and 2. Believes that the problem might have been the electrical problem. Please understand that the oil pressure switch does goes directly to the dashboard light, nothing-in-between other than wiring to give a false signal!
There are several reports of this problem on the web.
I have not tried Castrol, but did change the oil about 1 month ago to Mobil 1 and an OEM filter.

I am awaiting an answer from the BMW dealer.
 

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I'm surprised no one has mentioned checking and ensuring there is a good ground connection. As a test, run a wire from the ground portion of the switch and run it back to the neg side of the battery. See if that helps. It seems as though these sensors/switches etc really like good ground.
 
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