Hi

So one morning i got the dreaded message "high battery discharge rate" . In the evening, battery dead.

Exide battery, OEM, 90Ah, 10 months old. Ok i said this is the IBS sensor, although car is LCI N52 engine . I could see the serial number of it in INPA but when i removed the ground lead 4-5 times i think i broke it ? now INPA shows 000000 to serial ID and all that info.

Bought a new battery AGM, 95Ah, removed the IBS connector from the sensor, now alternator won't charge above 13.1 v whatever i do (shut down A/C, lights), rev it up to 3000 rpm, only 13.1/13.2 which is low.

I disconnected the battery , i am afraid that i will ruin this one too. No other codes on DME or on other module except 2e7c BSD communication error

I checked the cables from the IBS, i have +12v on the red cable, i have +12v on the grey / green ? cable . The other is the BSD cable. Also i checked the IBS pins and they are not shorted to ground or to +12v or to each other on the BSD line.

Checked alternator connector, everything looks fine. Nobody worked on the car lately. I don't know where to check the oil level sensor .

From the diagrams, i see that Oil condition sensor and alternator go to DME pin 35 , and IBS is a different connector altogether with the DME. I don't see that the water pump is connected to the BSD line, maybe on other engines is but not mine.




IBS

How the BSD line works, if one device is not connected, it will shutdown all the others , regardless if their connection and sensors are working ?

Thanks


Later Edit: Pulled out alternator BSD connector, now everything is back to normal, i can see the IBS, oil level works. I believe the voltage regulator is faulty, disrupting all BSD line components including the water pump, which probably stayed on for a long time hence the dead battery.

 

Resurrecting thread.

So, things done:
- changed water pump, thermostat (car has 150000km so, it was time more or less)
- changed alternator regulator (original regulator looked good, decent amount of brushes left)
- new Bosch S5 AGM battery

When mechanic tried to start the car after above operations, surprise: no crank

So the culprit was a defective starter that would steal power. (because the starter doesn't go to sleep mode ). Paradox is, that there were no signs of fatigue on the starter, it worked flawlessly.

Now i have a car with new starter, water pump, thermostat, and half alternator, but better to be safe than sorry .

 

Great info. Thanks for the follow-up post!