[jojojijijojo]

Hi all,

Im facing yet another dilemma with my e92.

Engine oil sensor reads INACTIVE all the time, and the car feels extra sluggish and wants to die at red lights.

After 2 days of sitting, the battery is almost dead and I cannot start the engine.

I charged it back to about 13.5v and car started fine but sensor still reads INACTIVE.

After a long day of driving, the battery is supposedly in good charging state.

Next day, everything is dead, not even the key fob works, battery went down to 8v(yucks).

So apparently there is something electrically shorted that's draining up my battery, improper engine grounding resulting in rough idle, and the oil sensor inactive. Any clues where to start looking?

[JonOhh]

Water pump, cooling fan, oil sensor, and battery monitor (ibs) are all on the same communication bus (BSD). One of those has likely shit itself and is preventing communication between the dme (the interpreter of the BSD line) and the aforementioned components.

Common causes are the IBS itself, and oil getting inside the oil level sensor connector and shorting the BSD line to ground or high voltage. The water pump electronics and connector can also fail/become contaminated (respectively) and cause an identical condition.


Is your water pump running continuously after shutdown? It should run for a variable amount of time after shutdown, depending on temperature- so checking right after you shut it off won't tell you anything. If the coolant is cool enough to remove the cap slowly an hour or so after turning the car off, you can look down into the reservoir and see if there is coolant flow from the expansion tank line. Going by sound isn't good enough as the N52s pump is damn near silent at lower speeds.

I am inclined to believe it is either the water pump never shutting off, or the BSD inhibiting battery charge.

I do believe that the dme limits engine output (or alters operation in some way) when it is unable to communicate with the modules that make up the cooling system, but it's been so long since I've looked at any of that stuff I can't remember. I can most definitely be wrong about this but it's the only explanation for power loss that I can think of- apart from a running hotter than target condition caused by the inability to adjust water pump speed. I would think the failsafe would be full pump speed but I don't know for certain, so I figured I'd mention it.

I hope this helps you work towards a solution,

Jon

[jojojijijojo]

Thanks a lot for the tips. I think what you are guessing is right, I just still wasn't able to pin point where the fault is exactly.

Prior to this the car has been power washed, and I think they also power washed it from the bottom when it was on the lift to remove oil stains.

Today I jacked it up and removed the under tray, I unplugged the connector to the oil sensor hoping I would find water creeping there, but it was dry. I sprayed the male/female connectors with cleaner and blasted it with air. Connected it back in but the problem is still present.

[dpaul]

Originally Posted by JonOhh

Water pump, cooling fan, oil sensor, and battery monitor (ibs) are all on the same communication bus (BSD). One of those has likely shit itself and is preventing communication between the dme (the interpreter of the BSD line) and the aforementioned components.

I am inclined to believe it is either the water pump never shutting off, or the BSD inhibiting battery charge

FWIW the cooling fan is not controlled by the BSD bus. The relevant components are water pump, alternatior, oil sensor, IBS and of course, the DME. In addition, an IBS problem would be irrelevant to the OP's report that that car ran fine after charging but the battery discharged overnight (when the engine is not running and no charging is taking place).

OP - there are all kinds of explanations for your issues but you don't need to do so much guessing. Install BMW standard tools on your laptop and read the codes. Or at least buy a cheap code reader and read the codes. Or take the car to Autozone and get them to read the codes. Just read the codes, one way or another. That is ALWAYS the first place to start.

[jojojijijojo]

Originally Posted by dpaul

FWIW the cooling fan is not controlled by the BSD bus. The relevant components are water pump, alternatior, oil sensor, IBS and of course, the DME. In addition, an IBS problem would be irrelevant to the OP's report that that car ran fine after charging but the battery discharged overnight (when the engine is not running and no charging is taking place).

OP - there are all kinds of explanations for your issues but you don't need to do so much guessing. Install BMW standard tools on your laptop and read the codes. Or at least buy a cheap code reader and read the codes. Or take the car to Autozone and get them to read the codes. Just read the codes, one way or another. That is ALWAYS the first place to start.

Thanks for the tips. Yes the car runs fine after I charge the battery, so no IBS issue, also the battery is in good charging state after I get back, so no alternator issue either. Discharge happens overnight when its sitting locked. Water pump is functioning correctly, I can do the bleeding procedure just fine, and engine temperature is fine.

Is there a fuse for the oil sensor? I'm thinking about pulling out its fuse and see if the discharging problem continues.

I had a K+DCAN cable that I normally use with my laptop but it's nowhere to be seen, I will eventually get to it after I do the final test of unplugging the oil sensor fuse.

[dpaul]

Originally Posted by jojojijijojo

Thanks for the tips. Yes the car runs fine after I charge the battery, so no IBS issue, also the battery is in good charging state after I get back, so no alternator issue either. Discharge happens overnight when its sitting locked. Water pump is functioning correctly, I can do the bleeding procedure just fine, and engine temperature is fine.

Is there a fuse for the oil sensor? I'm thinking about pulling out its fuse and see if the discharging problem continues.

I had a K+DCAN cable that I normally use with my laptop but it's nowhere to be seen, I will eventually get to it after I do the final test of unplugging the oil sensor fuse.

Yes there is a fuse. The location and number depends on the date of manufacture and engine type. Post that info and the 7 last characters of the VIN and I can find out for you.

BTW, if you had ISTA-D installed on your laptop, you wouldn't need help - you could look up the wiring diagram yourself as well as perform diagnostic tests that might point you more directly to the problem.

[JonOhh]

Originally Posted by dpaul

FWIW the cooling fan is not controlled by the BSD bus. The relevant components are water pump, alternatior, oil sensor, IBS and of course, the DME. In addition, an IBS problem would be irrelevant to the OP's report that that car ran fine after charging but the battery discharged overnight (when the engine is not running and no charging is taking place).

OP - there are all kinds of explanations for your issues but you don't need to do so much guessing. Install BMW standard tools on your laptop and read the codes. Or at least buy a cheap code reader and read the codes. Or take the car to Autozone and get them to read the codes. Just read the codes, one way or another. That is ALWAYS the first place to start.

Can confirm, you are entirely correct. The fan is NOT on the BSD bus as I thought it was.

[jojojijijojo]

I pulled the oil sensor fuse (11) which has many other things connected to it as well like the MAF sensor etc.. I left the battery plugged in and locked the car, next morning it is dead again. I did not use the car that day and the water pump was supposedly off.

There is definitely something draining up power and most likely its not the oil sensor. It showing as inactive is a clue tho.

Does anyone have a diagram of what electrical plugs are there underneath the car? Its a 2010 E92 n52 engine. This power drainage started happening as soon as the car had an extensive undercarriage power wash.

[ptpending]

water pump usually can drain the power, this one of the way they die

[jojojijijojo]

Originally Posted by ptpending

water pump usually can drain the power, this one of the way they die

Im going to get an amp meter today and start unplugging fuses one by one while the car is sleeping and hopefully see where the parasitic drainage is.

[ptpending]

you can charge battery
remove connector from pump
leave car for night
and measure the battery next day

[gbalthrop]

Originally Posted by jojojijijojo

Im going to get an amp meter today and start unplugging fuses one by one while the car is sleeping and hopefully see where the parasitic drainage is.

As others have suggested: FAULT CODES PLEASE!

If properly-charged battery is drained to point of NOT cranking starter in 8 to 10 hours, that is such a large Parasitic Draw/ Quiescent Current, that a DC Current Clamp meter ($35 to $40) would clearly show which of the 3 large Red B+ cables is carrying that current. Check the cable going to Jumpstart Terminal (LARGE B+ Cable at (+) Battery Terminal).

Most likely cause of LARGE Parasitic Draw is failed Alternator Diodes. Quick/Cheap way to check that: Leave hood unlatched when you shut off engine. Come back in two or three hours and open hood. Feel rear of alternator for heat. If it is hot to the touch (moreso than the front of crankcase), then the alternator is almost certainly the culprit.

Put Clamp Meter on the "Medium-sized" cable from rear of Power Distribution Panel on top of battery, that goes up and over battery to Harness that runs INSIDE the vehicle. That goes to the JB (Junction Box) Fuse Panel. If that is showing 1+ Amp DC Current, then pull the 30G Relay (large black relay on R side of JB Panel). See if Current decreases to near-zero.

Please let us know what you find,
George

[jojojijijojo]

Originally Posted by gbalthrop

As others have suggested: FAULT CODES PLEASE!
If properly-charged battery is drained to point of NOT cranking starter in 8 to 10 hours, that is such a large Parasitic Draw/ Quiescent Current

Yes from fully charged to around 9v overnight, something is terribly shorted out, I wish I could get codes but I still don't have the tool and can't drive it without it dying on me.

I will do your suggestions and get back with some results.

[jojojijijojo]

I did a quick test and overall power drain from battery when everything is locked is around ~17 amps, after a couple of minutes it slowly goes down to ~10 amps and stays like that.

Next I unplugged the blue and red cables shown circled in the image, and power drain remains the same, it seems that the big red cable marked with a black arrow is what's sucking all the juice. I believe that's the one going to the junction box?

[gbalthrop]

Originally Posted by jojojijijojo

I did a quick test and overall power drain from battery when everything is locked is around ~17 amps, after a couple of minutes it slowly goes down to ~10 amps and stays like that.

Next I unplugged the blue and red cables shown circled in the image, and power drain remains the same, it seems that the big red cable marked with a black arrow is what's sucking all the juice. I believe that's the one going to the junction box?

Do you have a "Clamp Meter" capable of reading DC Current (Amps)?
Where & HOW did you measure "17 amps" or "10 amps" current draw?
"Scientific Testing" with proper equipment is intended to ELIMINATE "seems".

If you have a Clamp Meter that can read DC Current via the clamp, clamp it on the cable with black arrow. That Cable DOES go to the Junction box. If the Clamp Meter shows > 1 Amp DC Current, then pull the 30G relay on the right side of JB Fuse Panel in front of Glovebox (large, black relay), and see if DC Current Draw changes.

Did you "Feel" the rear of alternator for heat several hours after shutdown as suggested in earlier post? The suggested tests are designed to eliminate possible causes. We're NOT doing that so much.
George

[jojojijijojo]

Originally Posted by gbalthrop

Do you have a "Clamp Meter" capable of reading DC Current (Amps)?
Where & HOW did you measure "17 amps" or "10 amps" current draw?
"Scientific Testing" with proper equipment is intended to ELIMINATE "seems".

If you have a Clamp Meter that can read DC Current via the clamp, clamp it on the cable with black arrow. That Cable DOES go to the Junction box. If the Clamp Meter shows > 1 Amp DC Current, then pull the 30G relay on the right side of JB Fuse Panel in front of Glovebox (large, black relay), and see if DC Current Draw changes.

Did you "Feel" the rear of alternator for heat several hours after shutdown as suggested in earlier post? The suggested tests are designed to eliminate possible causes. We're NOT doing that so much.
George

Yes sorry I was not clear, I used an amp meter to get the current measurements.

~17 to 10 amps was going through the big junction cable.

There was no heat behind the alternator.

I pulled off the 30g relay and power draw dropped to about 0.6 amps.

When I tried to put back the relay I forgot I still had the battery hooked, so the relay kinda screamed a bit. After I shook it things seemed to go back to normal, with 0.6amps draw the first 30minites, then 0.1amps afterwards.

0.1 is still no good, but at least we are getting there.

I'm going to check it in a bit and see where the voltage is at, oil sensor is still K.O tho.

[gbalthrop]

Originally Posted by jojojijijojo

... I used an amp meter to get the current measurements. [Did you use a CLAMP Meter, or did you open the circuit and put a conventional Amp Meter in Series with the JB Supply B+ Cable?] ~17 to 10 amps was going through the big junction cable...
I pulled off the 30g relay and power draw dropped to about 0.6 amps.
When I tried to put back the relay I forgot I still had the battery hooked, so the relay kinda screamed a bit. After I shook it [shook the relay?] things seemed to go back to normal, with 0.6amps draw the first 30minites, then 0.1amps afterwards. [Clamp meters may NOT be accurate measuring DC Current < 100 mA (.1 Amp).]
0.1 is still no good, but at least we are getting there...

Please provide Last-7 Characters of your VIN so I can provide correct ISTA wiring diagrams for your vehicle.

I will provide a list of fuses which are "switched" by the 30G relay. You might Bench-Test that relay to see if it operates properly to open the contacts (remove power from switched fuses) when activation current is removed from electromagnet.

If you have any questions about how to do that, please attach a photo of 4 pins of relay, or otherwise identify pin numbers, such as 30, 85, 86, 87. Here is an example of a replacement 30G Relay. This is for my 2007 E91, so your proper part# might be different, depending upon your VIN.

Note the position and size of the four pins in the multiple views in this link. The two electromagnet pins are almost certainly the SMALLER pins on either side. Many relays (like one shown in photos on link) have a circuit diagram showing electromagnet pins.
https://www.ecstuning.com/b-genuine-...k/61366901469/

George

[jojojijijojo]

Some more updates, while the battery is disconnected, I did a continuity test between the negative terminal and the B+ Junction box cable and it is indeed shorted, resistance shows as 9.2 ohms.

Now with the multimeter hooked, I went to the gloves box fuses and pulled one by one until I got to fuse 41, when I pulled it out there was not more short.

I traced f41 and it seems to be related to door windows. I unplugged the footwell frm module, however the short is still there, so fortunately its not the footwell module.

From schematics ( my car is n52 e92 2010 so from 2007 upwards) I found that fuse 41 is carried by x11005 through pin 2.

Now most likely the short is happening along the path of pin 2 at x11005 connector. Looking further it seems that the same pin is feeding dsc?

Thats where Im at now.

[jojojijijojo]

Wait my bad, discard what I said previously, its actually F38 not F41 that's causing the short. Now back to searching.

[jojojijijojo]

Ok so F38 feeds 3 components Crankcase breather heating ,Engine control module (ECM), and Oxygen sensor heating.

Tracing down f38, it goes to x8680 connector pin 8, which interesting enough, is close to pin 6 on the same connector and that powers the oil sensor.

f38 also goes to x11005 through pin 5 then to x6011 through pin 4 then to x60551 through pin 3 which then feed the oxygen sensors and crankshaft breather heating.

More tracing underway.

[gbalthrop]

[QUOTE=jojojijijojo;28828811]Wait my bad, discard what I said previously, its actually F38 not F41 that's causing the short. Now back to searching.

Originally Posted by jojojijijojo

Ok so F38 feeds 3 components Crankcase breather heating ,Engine control module (ECM), and Oxygen sensor heating.

F38 on your 2010 model supplies (1) the four O2 Sensor Heaters, & (2) the Breather Heater. It does NOT supply the DME.

There have been TWO recalls related to the Breather Heater, the most recent being 22V-119, for which current E9x owners, properly-registered with BMW, have just received new notice of recall. "Remedy is Unavailable" at this time.

HOWEVER, F38 is NOT powered UNLESS Ignition ON and K6300 (DME Main Relay) is activated. So if you have Parasitic Draw with Ignition OFF, F38 circuit (or any other circuit with fuse powered via K6300) CANNOT be causing the draw, UNLESS K6300 is stuck with contacts closed. F37 (which supplies DME) and F39 are both powered via K6300 DME Main Relay.

So if there is 12V+ at one of the sockets of each of those three fuse sockets (F37,F38,F39) with fuse REMOVED, and Ignition OFF, then your DME Main Relay is stuck in activated position (contacts closed).

If you need specific Info, including ISTA wiring diagrams, please provide Last-7 Characters of VIN.
George

[jojojijijojo]

Thanks for the valuable information George. Right now, with battery detached, resistance between ground and B+ junction cable shows 9ohms (basically shorted out), when I remove f38 the short is gone. What could possibly be causing this?

It's good to know that those fuses are only energized when ignition on, I will definitely test that later on, but for now I don't understand why f38 is shorted to ground.