[PhaceN52]

Hi,

Sorry for the long post, I hope some of you can have an idea on what could cause this, I'm lost. So I'm having this problem since a few weeks and still trying to trace it down to something: one day from out of nowhere the oil level sensor said "Inactive" on the dash while i knew it was at -750ml (I check it quite often), so near the +1 quart/liter mark, and after a few restarts it was back again reading correctly. I topped the oil, went for a drive and it said oil OK, then after a restart it went again to inactive and stayed there.
Did two weeks of mostly short trips and some longer ones while noticing that the voltage reading on the dash secret menù was oscillating between 13.4/13.7 volts, a bit lower than what it used to put out that was 14/14.3v. The battery is a 10 month old Bosch 100Ah non AGM, like the old one in the car.

During this time there was also a small crack on the radiator that now I've replaced, but needing to top off the coolant quite often I did the water pump bleeding procedure like 6/7 times, and every time it went through the bleeding steps cycles, blasting coolant at low and high pressures, until the last time after I installed the new rad: water pump seemed to operate full blast only, so after a few minutes I just shut off the ignition and topped up.

INPA shows some BSD errors, these were present before the radiator replacement
2EC7 BSD, signal
2E8B IBS missing
2EEA coolant temperature sensor
2EEB coolant temperature sensor

Reading some threads on here it appears that there's something on the BSD line preventing normal communication but I don't have any water pump/alternator codes

Used contact cleaner on the oil sensor connector, nothing. Replaced lower coolant hose temperature sensor while doing the radiator since it was like 6$, nothing; battery still seemed strong, it also went through an INPA DSC bleed in the meantime.

After a week all of a sudden the car FULLY drained the battery in like 1 day, central locking not working, the dash menu was reading 6v
Had to desulphate the battery since it won't charge normally, put it back this morning and it's all good again, but there's clearly something that won't shut off or badly shorted, what can I do?
Do you think a bad voltage regulator could cause a BSD error and indirectly drain the battery leaving the water pump on after shut off?

This afternoon I'll try some tests advised in this topic
N52 oil sensor Inactive + abnormal battery drain

while reading codes again, I'll report back
Thank you all

[PhaceN52]

Ok so the only codes that reappear every time are

• 2E7C Bit Serial Data signal, communication error - this one everytime as I start the car
• 2DEC Battery monitoring Deep Discharge
• 2E8B INS signal - Voltage at IBS 13.87v, at KI.87 13.41v (INPA freeze frame data)

Again, nothing from the waterpump or alternator
In INPA , on the CAS ignition diagnose page, there are two voltages flickering around, hall12 and hall34, anyone knows what are they? (Video)
No matter if key is inserted or not, as nothing changed when I disconnected the water pump discovering that a pin on the connector had fryed out this wasn't the case before the huge battery drain, when I replaced the radiator I checked that connector and it was ok. It's the pin for the big red wire, I think the 12v
Checked the dme box and it's totally dry

gbalthrop Sorry if I'm bothering you George, please, what do you think?

Thank you all

[Daaaaaaaan]

When the coolant pump doesn't get BSD communication, it will go into "fail-safe mode" and run at full power continuously. Is it running all the time once you put the key in? At full power all the time, I'm guessing it started burning out the connector , but it does seem kinda fast to start burning out, but I can't think of any other explanation (other than something like a short causing it to draw more current, but then your fuse would blow?).

But the root cause problem may or may not be your water pump. Is the water pump original? Other things on the BSD bus: could be IBS sensor, could be alternator (which should really be charging at a higher voltage I think?), could be oil sensor, could still be coolant pump or could be a wiring issue (like a short) or bad DME.

I know he uses a scope on the IBS bus, and if you just measure it with a voltmeter, it will still average out to 0V even when it is working properly and not tell you anything, *but* if you have a simple 1n4148 diode in series, you could measure and just see if there's a positive voltage on the IBS bus or if it's actually stuck at 0V, but as the video shows, you can unplug stuff and use the non-stop coolant pump as your guide: it should shutdown when BSD comms resume.

(I think an piezo speaker ripped off an ancient computer's motherboard might also help in determining if a waveform is present. I wonder if a headphone speaker could work too... just thinking aloud here)

Keep your battery charged up as much as possible at all times!

[LonnieBrakus]

Having a video tutorial makes it much easier to understand.

getting over it

[PhaceN52]

Just an update, after catastrophic scenarios in my mind like dme and so on it was obviously the water pump that was starting to break without throwing related codes, it destroyed itself some days ago with the usual symptoms of radiator fan on full blast and yellow overheating symbol on the dash, now waiting for the new part.. I'll update again

[PhaceN52]

Yes, it was the water pump electronics going bad months before it failed completely. Never had a direct code pointing to that, BSD errors are all gone now and the oil sensor reads normally. Broken wp was a Pierburg that lasted about 12 years, we'll see how will behave the new one, a renowned MOSTPLUS