Oil Sensor is defective and odd up and down idle

[rmousir]

Hi all,

Could use some help here today. I've been searching the forum and haven't found anything exactly right.

First the car:
2006 Z4 3.0si auto

OK.. the back ground. I had a dead battery issue. I traced this down to a bad alternator. I disconnected the battery for a week while my alternator was shipped in. I installed the alternator and fired up the car.

I noticed right away three things.

1. immediately after starting the car, the revs jump up and down a little and continue to do so when I'm at a stop light or when ever the car is at a stand still. Drives fine.

2. my clock needs reset, which I expected.

3. when checking my oil I get the message 'Error Oil' which from reading the manual means: The oil level sensor is defective: it is not possible to issue a current or accurate measurement.

#1 and #3 are concerning to me. The car ran fine before I had the alternator fail. I'm wondering if I need to do some sort of a reset or something. I have done several google searches but I haven't found anything solid and for the Z4.

Any suggestions, direction, or comments are most welcome.

Thank you in advance for any help you can provide.

Richard.

[Punisher3.0si]

1. The computer might have to go through a relearn to fix that.

2.

3. I've never heard of this problem before. Must be pretty rare. I'll check out if there is any known fixes for that at work today.

[rmousir]

That was excellent! I'll get the time set no problem.

I'll leave the car for a bit and see if the computer 'learns' on the idle.

Anything you can find on the oil sensor would be greatly appreciated.

Thanks very much.

[Punisher3.0si]

Your welcome

So I looked into it and believe it or not you might have a bad alternator. The oil level sensor and alternator are tied in to each other through the network.

[rmousir]

Originally Posted by Punisher3.0si

Your welcome

So I looked into it and believe it or not you might have a bad alternator. The oil level sensor and alternator are tied in to each other through the network.

I did have a bad alternator.. which is what I just changed this weekend. Brand new alt.

How are they connected?

[Punisher3.0si]

Yeah I know I read what you wrote. Just because it's new that doesn't mean it's good. I've learned that lesson the hard way lol. The Alternator and oil level sensor both communicate on the BSD network. This allows the alternator to have smart charging capabilities. The fact that the oil level sensor was previously working and now it doesn't after the alternator was replaced tells me that the problem is probably in that area.

[rmousir]

Originally Posted by Punisher3.0si

Yeah I know I read what you wrote. Just because it's new that doesn't mean it's good. I've learned that lesson the hard way lol. The Alternator and oil level sensor both communicate on the BSD network. This allows the alternator to have smart charging capabilities. The fact that the oil level sensor was previously working and now it doesn't after the alternator was replaced tells me that the problem is probably in that area.

OK.. so they are tied into the same system.. Is there a way to test the sensor or the alternator to see where the defect is at? I'll check the alt out but I'm unaware of any test that would indicate anything with the sensors of any time.. however, I've got a lot to learn.

[Punisher3.0si]

That's what the schematic looks like. They are spliced together on the same wire for the network.

[Punisher3.0si]

You can try disconnecting the alternator and see if the oil level portion works through the dash. If it does then you know the alternator is screwing up the network.

[rmousir]

Originally Posted by Punisher3.0si

You can try disconnecting the alternator and see if the oil level portion works through the dash. If it does then you know the alternator is screwing up the network.

excellent.. i will do that.. I'll try that today. I'll report back with what I find..


regarding the idle revs.. This is a learned condition then and the computer will eventually smooth that out?

[rmousir]

Originally Posted by Punisher3.0si

You can try disconnecting the alternator and see if the oil level portion works through the dash. If it does then you know the alternator is screwing up the network.

Well I tried this yesterday. Luckily its really easy to get to the alt on the car. I fired up the car with the alt connected like normal and sure enough the error is still there.. so I shut down the car. disconnected the alternator, turned the key to the on position, but didn't start it. And hit the oil sensor button and it shows everything is OK!

I was tickled pink!

So I called my local part store where I bought the alt.. Spoke to the asst manager, who happens to be a bmw fan and she has already ordered in a new alternator for me. I swap it out on Friday. With luck, this will resolve my issue.

Thank you very much for that... I'll report back after that..


Any thoughts on the irregular idle? I'm wondering if its related?

[Punisher3.0si]

Awesome that's good to hear! That can definitely cause the irregular idle. What brand was it? I've had issues with using advance auto specials before on European cars.

[gas-can]

FYI - that oil sensor has 2 distinct modes - one for when the engine is on (static analysis) and one for when engine is running.

If the oil reading worked when the engine was off (b/c you had no alternator connected), you may still have a faulty oil sensor - it may just be the dynamic part that's faulty.

If you have the diagnostic software, you can ask the computer to give you the reason why it failed the check in the first place.

Just to keep you informed!
-gc

[rmousir]

Originally Posted by gas-can

FYI - that oil sensor has 2 distinct modes - one for when the engine is on (static analysis) and one for when engine is running.

If the oil reading worked when the engine was off (b/c you had no alternator connected), you may still have a faulty oil sensor - it may just be the dynamic part that's faulty.

If you have the diagnostic software, you can ask the computer to give you the reason why it failed the check in the first place.

Just to keep you informed!
-gc

I have a obd2 error code reader.. is that what your referring to? Is there something else I should be looking at buying?

Thanks.

[rmousir]

Originally Posted by Punisher3.0si

Awesome that's good to hear! That can definitely cause the irregular idle. What brand was it? I've had issues with using advance auto specials before on European cars.

Hi,

Alrighty.. I picked up a second alternator from my local part show.. exchanged it no problem.. took out the old new one.. ran the oil test (i have video if that helps) and it the oil checks out fine. Installed the new alternator and turned the key to the on position and ran the oil test.. took a while this time, and still ERROR (I have a video as this as well if it helps)..... So is that a solid enough test to assume I need a new oil sensor?

Thanks..

[gas-can]

Sorry to hear that Rmous. I was kinda expecting that though...

If it really is the oil sensor, it's actually an easy job. Bit messy though, since even after draining all the oil in the pan via that bolt, you still have some where the sensor is (it's lower). Recommend having something to catch it when you remove it. Also, remember to replace the o ring (if it doesn't come with the sensor).

With regards to software, I'm not sure if your OBD computer can pull this data - bmw uses its own data scheme for diagnostics so this code might be unrecognizable to your computer. What a lot of us use is a diagnostic clone of the actual software that BMW dealers use.

Here's one I got (no affiliation). Bit convoluted install but it works well.

Plus, in another question you asked about a repair manual. This software has the complete manual, which is indispensable for working on these cars.

Let me know if you have any questions!

-gc

[Punisher3.0si]

Originally Posted by rmousir

Hi,

Alrighty.. I picked up a second alternator from my local part show.. exchanged it no problem.. took out the old new one.. ran the oil test (i have video if that helps) and it the oil checks out fine. Installed the new alternator and turned the key to the on position and ran the oil test.. took a while this time, and still ERROR (I have a video as this as well if it helps)..... So is that a solid enough test to assume I need a new oil sensor?

Thanks..

Without a good scan tool it's a guess at this point

[Efthreeoh]

OP, the oil level sensor is a simple device that rarely malfunctions. If it has failed, there will be a diagnostic trouble code stored in the ECU. The static level measurement is achieved by simple flooding of the sensor (i.e. it is bathed in oil), so since you are getting a reading of "OK" for the static reading it seems the sensor electronics are working. The sensor is just a two-level capacitor, where the lower capacitor measures oil quality, and the upper capacitor measures oil level. The capacitors are just concentric metallic sleeves in which the engine oil acts as the dielectric (of the capacitor), so there is really nothing to "break" in the sensor except the electronics, which convert the capacitance measurements to a signal the ECU can understand. If the static reading is working, then the electronics are working.

I think what may be the issue is the ECU has "lost" the previous (last) oil level reading stored since the battery was disconnected for some time period. So since the ECU can't determine a previous oil level, it is probably showing a false fault in the oil level system. The N52 was retrofitted to the E85/86 chassis, so the electronics interface may be limited with the Z4 (just a guess). The oil sensor is expensive, about $200. There is a long story associated with my experience with the oil sensor (you can read up on it over at E90 Post), but the short story is I thought my senor was bad and changed it out (I published a DIY on how to replace the sensor on E90 Post), but it didn't solve my problem. I've discussed at length on how the sensor works and how to diagnose it with a dealership master technician. You need to scan the car to find if there is a fault with it.

I suggest, if you know the engine oil level is at or above the 6 quart minimum capacity, I would put the car back together and drive it for awhile to let the ECU reestablish an oil level. The ECU establishes a new oil level as follows:

Dynamic oil level measurement begins when following values are reached:
• Engine temperature > 60°C
• Engine speed > 1000 rpm
• Transverse and longitudinal acceleration < 4-5 m/s2
The transverse acceleration signal is supplied by the DSC. The longitudinal acceleration
is calculated from the speed and time factors.
• Increase < 5% after covering a distance of app.. 200 m. The increase value is
detected by the ambient pressure sensor in the DME.
On reaching this value, the oil level indicator is updated approximately 5 minutes after
starting vehicle operation. The oil level is then continuously measured. The indicator is
updated at 20 minute intervals. The "Check oil level" menu in connection with the
dynamic oil level measurement is exited while driving (vehicle speed > 0) app.. 15 seconds
after the oil level is displayed.

If no reading is still present, then have the car scanned with a BMW scan tool that reads BMW fault codes. Any decent Indy should scan the car for a reasonable charge and a lot less than $200 for a new sensor. If it were me I'd get the ECS Schwaben BMW scan tool (I just got one), before I'd take a chance on a new $200 sensor. If you are going to DIY this car in the future, having a diagnostic scan tool is as important as a good set of Torx sockets. The ECS scan tool is great because it also scans OBD2 systems, so it works with any car built after 1996.

I've attached training material on the N52. Page 48 starts the description on how the oil sensor works. If the oil sensor worked before the oil alternator failed, then if nothing electrically or physically damaged the sensor, logic dictates it should work afterwards. It could seem that the new alternator may be able to damage the oil sensor electrically since they are tied on the same buss, but if the alternator did damage the electronics of the sensor, I'd then expect the sensor not to be able to provide the static oil level reading.

Good luck with it.

[rmousir]

Originally Posted by Efthreeoh

I think what may be the issue is the ECU has "lost" the previous (last) oil level reading stored since the battery was disconnected for some time period. So since the ECU can't determine a previous oil level, it is probably showing a false fault in the oil level system. The N52 was retrofitted to the E85/86 chassis, so the electronics interface may be limited with the Z4 (just a guess). The oil sensor is expensive, about $200. There is a long story associated with my experience with the oil sensor (you can read up on it over at E90 Post), but the short story is I thought my senor was bad and changed it out (I published a DIY on how to replace the sensor on E90 Post), but it didn't solve my problem. I've discussed at length on how the sensor works and how to diagnose it with a dealership master technician. You need to scan the car to find if there is a fault with it.

I suggest, if you know the engine oil level is at or above the 6 quart minimum capacity, I would put the car back together and drive it for awhile to let the ECU reestablish an oil level. The ECU establishes a new oil level as follows:

Dynamic oil level measurement begins when following values are reached:
• Engine temperature > 60°C
• Engine speed > 1000 rpm
• Transverse and longitudinal acceleration < 4-5 m/s2
The transverse acceleration signal is supplied by the DSC. The longitudinal acceleration
is calculated from the speed and time factors.
• Increase < 5% after covering a distance of app.. 200 m. The increase value is
detected by the ambient pressure sensor in the DME.
On reaching this value, the oil level indicator is updated approximately 5 minutes after
starting vehicle operation. The oil level is then continuously measured. The indicator is
updated at 20 minute intervals. The "Check oil level" menu in connection with the
dynamic oil level measurement is exited while driving (vehicle speed > 0) app.. 15 seconds
after the oil level is displayed.

If no reading is still present, then have the car scanned with a BMW scan tool that reads BMW fault codes. Any decent Indy should scan the car for a reasonable charge and a lot less than $200 for a new sensor. If it were me I'd get the ECS Schwaben BMW scan tool (I just got one), before I'd take a chance on a new $200 sensor. If you are going to DIY this car in the future, having a diagnostic scan tool is as important as a good set of Torx sockets. The ECS scan tool is great because it also scans OBD2 systems, so it works with any car built after 1996.

I've attached an training material on the N52. Page 48 starts the description on how the oil sensor works. If the oil sensor worked before the oil alternator failed, then if nothing electrically or physically damaged the sensor, logic dictates it should work afterwards. It could seem that the new alternator may be able to damage the oil sensor electrically since they are tied on the same buss, but if the alternator did damage the electronics of the sensor, I'd then expect the sensor not to be able to provide the static oil level reading.

Good luck with it.

THANK YOU SO MUCH for posting that info. I have a ODCII reader and I have used it a few times already. I did put the car back on the road this weekend and it didn't have any issues. I am 100% confident that there is no problem with the oil level so I will drive the car.

I will also purchase this "ECS Schwaben BMW scan tool ". Did you get yours here: https://www.ecstuning.com/Search/Sit...ool/ES2975699/

Currently there is no check engine light. Will there still be a code? I assume checking the system with this BMW scan tool, I can check that specific system, right?

I am all set for tools including torx sockets. Looking to hear from you to be sure that is the correct ECS scan tool.. I will purchase it. I really like the idea of being able to test the systems in the car myself. With luck I will have this car for a long while. I also plan on buying a Kwiklift.

Thanks
Richard.

[Efthreeoh]

Originally Posted by rmousir

THANK YOU SO MUCH for posting that info. I have a ODCII reader and I have used it a few times already. I did put the car back on the road this weekend and it didn't have any issues. I am 100% confident that there is no problem with the oil level so I will drive the car.

I will also purchase this "ECS Schwaben BMW scan tool ". Did you get yours here: https://www.ecstuning.com/Search/Sit...ool/ES2975699/

Currently there is no check engine light. Will there still be a code? I assume checking the system with this BMW scan tool, I can check that specific system, right?

I am all set for tools including torx sockets. Looking to hear from you to be sure that is the correct ECS scan tool.. I will purchase it. I really like the idea of being able to test the systems in the car myself. With luck I will have this car for a long while. I also plan on buying a Kwiklift.

Thanks
Richard.

That is the correct scanner I was talking about. There are tons of choices other than the ECS unit too. So you can decide which one you should get. The ECS scanner is nice since it is OBD2 and BMW all in one handheld unit, powered by the OBD2 socket. Anyone owning a BMW and wanting of understanding their car should have a BMW scan tool IMO. Even if you don't DIY, knowing the trouble codes prior to taking the car in for repair helps weed through the possible BS you may get from less than honest repair shops.

[rmousir]

Originally Posted by Efthreeoh

That is the correct scanner I was talking about. There are tons of choices other than the ECS unit too. So you can decide which one you should get. The ECS scanner is nice since it is OBD2 and BMW all in one handheld unit, powered by the OBD2 socket. Anyone owning a BMW and wanting of understanding their car should have a BMW scan tool IMO. Even if you don't DIY, knowing the trouble codes prior to taking the car in for repair helps weed through the possible BS you may get from less than honest repair shops.

I ordered my scanner.. Should be here soon.

in the mean time I'm going to put some miles on the car. Should be more than enough for the computer to reset the oil sensor if it can. So I'll report back if after the weekend driving if the oil sensor is good to go or not.

[Efthreeoh]

OP, it's been a few weeks. What is the oil sensor reading now?