BSD Communication Fault

Aaron Owner/Technician Wisconsin Posted   Latest   Edited  
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Electrical
2011 BMW X5 M 4.4L (S63B44A) 6-spd (GA6HP26Z) — 5UXZV8C54BL420391
2E7c: Bsd Communication Fault
Cannot Read Oil Level

Hey all. I got hit with two BMWs with BSD faults this week! This one I am posting about is a 2011 X5 but DN did not have an option for the N63 engine, which this one has! It is NOT an S63. Ok so this car I began by running the test plan in ISTA and simultaneously checking the BSD line with a scope at the oil condition sensor. Sensor connected or disconnected, I have 0v. It is not shorted to ground either as resistance is like 900Mohms. If I disconnect the BSD connector on the alternator, I get a flat 5v, nothing is talking. No change plugging in or disconnecting the oil condition sensor. Now if I disconnect the IBS connector, the voltage just goes down to 2v. This is with the oil condition sensor plugged in or disconnected. If I go back to the alternator, plug it in and it all goes back down to 0v. I get these same values when checking the circuit at any of the three connectors, so I know the wiring between the all is good. During the test plan, the "fault is currently present" no matter what combination of sensors are plugged in or disconnected. This is just not making any sense to me. Any time I have checked BSD signals on other BMWs, its always a switching 0.5 to 13.5 signal. ISTA states that at least one sensor must be plugged in for the circuit to work. I don't know what that should look like if all were unplugged on a normal-functioning car, but I see 2v when all are disconnected. Let me know what y'all think! 

Thankyou

Aaron

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Aaron Owner/Technician
Wisconsin
Aaron Update
 

I did check the BSD on the second car I am working on: 2007 BMW 328i. That car the BSD was dropping from 12/0v down to 7/0v. Disconnecting all the components on that car, there was still a 12/0v signal coming from the DME. If these two BSD systems function the same, I should be able to check at the DME connector and see 12/0v. If I theoretically clipped the BSD lines near the DME to take out any…

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Aaron Owner/Technician
Wisconsin
Aaron Default
 

*I should add/clarify that the second car (07 328) was faulting when the voltage was down at 7/0v. Found very light corrosion in the DME connector (E-box cover was not on correctly). Cleaned corrosion and that is when the signal went to a normal 12/0v and cured the BSD fault. So then disconnecting everything on the BSD circuit and still having 12/0v should be a known good?

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Aaron Owner/Technician
Wisconsin
Aaron Update
   

Hi everyone. So I took this a bit further on the X5 with the flat, low voltages. I accessed the DME and checked voltage on both lines. The IBS has a gray wire that runs all the way to connector X60003 (pin 35). The Alternator & Oil-Condition Sensor both have a violet wire that gets spliced together in the engine harness on the right side of the head (I haven't actually seen it). This single…

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Anthony Technical Support Specialist
Pennsylvania
Anthony Default
 

Hi Aaron: Along with your wiring schematic, have you looked at this? newtis​.​info/tisv2/a/en/e70… Unless I am misunderstanding it, the SZL on the PT-CAN bus is used as a wake-up signal. Just a thought. HTH, Guido

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JB Owner/Technician
Minnesota
JB Default
 

Look at your BSD schematic. Start with only one component plugged in. Clear all faults, cycle the key and see if the code comes back. If it does not, disconnect the component that WAS connected and repeat this process until one of the components sets the fault when cycling the key. If none of them set the fault then you've got something else going on.

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JB Owner/Technician
Minnesota
JB Default
 

As a side note: if you had the oil level sensor connected and the square wave signal flatlines, check your power and ground to the sensor via load test. If you can … a 3157 bulb or similar and the Lin signal flatlines when you ONLY have the oil level sensor connected, try plugging in any other bsd component by itself. If the bsd now has a square wave (backprobed) then the oil level sensor is…

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Aaron Owner/Technician
Wisconsin
Aaron Default
 

Yes, I did try this; I tried every combination of having only one of the three components installed on the BSD line at a time. So I can say for sure that the alternator brings the BSD line down to 0v. If I have alternator and level sender disconnected, then I only have a flat 5 volts, no communication/data signal happening. This 5v is consistent at the DME, IBS, alternator's harness connector…

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JB Owner/Technician
Minnesota
JB Default
 

If the bsd is flatlining then no communication is being initiated by the master node (DME). I'd be looking at things connected to the DME that are shorted and also load testing power and ground to the DME. Do you have any CAS faults or DSC faults? Just to recap all components on the BSD: intelligent battery sensor, oil condition sensor, alternator, turbo coolant pump, and intercooler coolant…

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Aaron Owner/Technician
Wisconsin
Aaron Default
 

You know, I did not touch either of the coolant pumps. The wiring diagram that comes up in ISTA is "Interface Signals v.11". The test plan talks about checking only the wires that share "D-BSD". The turbo coolant pump is on "A-S-WUP" and the inverter coolant pump is on "M-LIN". Though after reading Anthony's link, I was starting to second guess that. I will get the X5 back in here as soon as I…

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Aaron Owner/Technician
Wisconsin
Aaron Default
 

Just disconnected both water pumps, no change to the flat 2v signal.

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Aaron Owner/Technician
Wisconsin
Aaron Default
 

Yea I'll check that out, thank you.

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Aaron Owner/Technician
Wisconsin
Aaron Update
 

Well I just found SI B12 18 12 referencing missing valve cover grounds. These grounds are part of the coil wiring harnesses. The vehicle came in with these grounds missing. I had installed new bolts not even knowing these were ground points, just assumed they were harness mounting bolts. This car came in with a list of things. I went in to replace the injectors first to cure a misfire. Anyway, I…

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JB Owner/Technician
Minnesota
JB Default
 

Yes the bsd should be 12v square wave. So a bad ground to the DME is possible. I'd be checking all powers and grounds to the DME. If they are all present (sounds like they're not), and they pass a load test with a sealed beam headlamp, then it needs a DME.

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Aaron Owner/Technician
Wisconsin
Aaron Delay
 

Hey all, so I checked the DMW power and grounds and all are good. I believe that the grounds that were missing from both banks of coils is what caused the DME and alternator to fail. Unfortunate the customer declined any repairs at this time. He is going to live with it for a while. If he decides to make a repair, I will definitely post the outcome. Thanks for the help.

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