2008 335I Interesting BSD bus issue

rw335i · 08-05-2020, 08:13 PM

Three hours after previously driving the car, I went out to start my car yesterday and couldn't even unlock the doors. The battery was down to 10.1V. After jump starting, I headed to the shop. I got about a mile and the overheat warning came on, first yellow then red. So I parked the car. With my cigarette lighter meter I had also noticed that my alternator was only putting out 12.9V. So I was thinking alternator or IBS. But the problem was something totally different. The water pump was working but had an internal leak that was wetting the electrical connector and causing a problem with the bus. Later I found that this corrected another issue. My car had been saying that I needed an oil change in 2100 miles even though I had just changed the oil. BTW, the battery is new.

P.S. I think it is BSD but I may have the bus name wrong.

gbalthrop · 08-05-2020, 11:23 PM

Yes, the Alternator, Coolant Pump, IBS & OZS (Oil Condition Sensor) are ALL on the BSD (Bit Serial Data) BUS, per this TIS wiring diagram:
https://www.newtis.info/tisv2/a/en/e...rnator/gShOnF9

I would NOT try to drive the vehicle until you have Read & Saved ALL Fault Codes and Freeze Frame Data saved in the DME, preferably with a Scan Tool or Software such as INPA that can read ALL "Hex-codes" including those related to the Coolant Pump. Reading ALL DME (Engine Control Module) Fault Codes is essential to proper diagnosis of the issue.

However, that said, any short to ground or other interference with the Violet wires shown in the schematic linked above can cause lack of proper signals TO, or receipt of data FROM, other components connected to the BUS. You describe a situation where Coolant Pump is leaking on its electrical Connector (X6035), and THAT can cause issues with the Alternator control by the DME via the BSD Bus, and/or IBS measurement/ reporting of battery Voltage.

If you had INPA to attempt control of the Alternator and Coolant Pump, using F6 "Activations"/Steuern, you could test each independently (with the other disconnected) to see if the DME can control each one as it should.

As you may be aware, the Alternator Voltage Regulator contains Diodes which can fail and cause LARGE Parasitic Draw after engine shutdown. Hopefully THAT is NOT the issue, but rather lack of proper Voltage Output due to BSD Bus issue, most likely caused by WET X6035 Connector @ Coolant Pump.

So you COULD simply try disconnecting Connector X6035 from the Coolant Pump, and then testing Alternator voltage (should be 13.5 to 14.8V when engine running) with Pump DISconnected.

Please let us know what you find,
George

08-05-2020, 08:13 PM	#1
rw335i New Member 4 Rep 6 Posts Drives: 2008 335i Join Date: Jul 2019 Location: durham, nc iTrader: (0) Garage List 2008 BMW 335i [0.00]	2008 335I Interesting BSD bus issue Three hours after previously driving the car, I went out to start my car yesterday and couldn't even unlock the doors. The battery was down to 10.1V. After jump starting, I headed to the shop. I got about a mile and the overheat warning came on, first yellow then red. So I parked the car. With my cigarette lighter meter I had also noticed that my alternator was only putting out 12.9V. So I was thinking alternator or IBS. But the problem was something totally different. The water pump was working but had an internal leak that was wetting the electrical connector and causing a problem with the bus. Later I found that this corrected another issue. My car had been saying that I needed an oil change in 2100 miles even though I had just changed the oil. BTW, the battery is new. P.S. I think it is BSD but I may have the bus name wrong.
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08-05-2020, 11:23 PM	#2
gbalthrop Brigadier General 2689 Rep 4,030 Posts Drives: 2007 328xi E91 Join Date: May 2017 Location: Fairfax Co, VA iTrader: (0)	Yes, the Alternator, Coolant Pump, IBS & OZS (Oil Condition Sensor) are ALL on the BSD (Bit Serial Data) BUS, per this TIS wiring diagram: https://www.newtis.info/tisv2/a/en/e...rnator/gShOnF9 I would NOT try to drive the vehicle until you have Read & Saved ALL Fault Codes and Freeze Frame Data saved in the DME, preferably with a Scan Tool or Software such as INPA that can read ALL "Hex-codes" including those related to the Coolant Pump. Reading ALL DME (Engine Control Module) Fault Codes is essential to proper diagnosis of the issue. However, that said, any short to ground or other interference with the Violet wires shown in the schematic linked above can cause lack of proper signals TO, or receipt of data FROM, other components connected to the BUS. You describe a situation where Coolant Pump is leaking on its electrical Connector (X6035), and THAT can cause issues with the Alternator control by the DME via the BSD Bus, and/or IBS measurement/ reporting of battery Voltage. If you had INPA to attempt control of the Alternator and Coolant Pump, using F6 "Activations"/Steuern, you could test each independently (with the other disconnected) to see if the DME can control each one as it should. As you may be aware, the Alternator Voltage Regulator contains Diodes which can fail and cause LARGE Parasitic Draw after engine shutdown. Hopefully THAT is NOT the issue, but rather lack of proper Voltage Output due to BSD Bus issue, most likely caused by WET X6035 Connector @ Coolant Pump. So you COULD simply try disconnecting Connector X6035 from the Coolant Pump, and then testing Alternator voltage (should be 13.5 to 14.8V when engine running) with Pump DISconnected. Please let us know what you find, George
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