[mtntrx]

TL;DR
bad transfer case?

• Purchased this as a project 2006 325ix
• I'm inexperienced with BMW, but have been reading a ton and learning ISTA
• trifecta on dash, no noise from transfer case
• 54C4 calibration errer
• 54C6 oil wear
• 54C8 Class Resistance at actuator

More diag:

• When I activate it manually with ISTA, it does about 4 3-second actions and then reports an error "A comm fault occurred during activation. Incorrect state: ERROR_ECU_GENERAL_REJECT"
• Actuator motor? I swapped it for a known good one with no change (fried had a few) -- I usually don't like the parts canon, but it was easy, available, and a common failure
• Untrained ear says it sounds like the actuator is spinning too far and giving up
• I can put my finger in there and move one of the cam-arms more than an inch before it puts up resistance. that seems too far.
• I can also (with one finger) easily rotate the actuator cam/gear maybe 20°
• The class resistor error is confusing to me about what it means. I know the ECU reads the R-value and adjusts its movements to accommodate for mfg tolerances in the t-case; but I don't know how it would determine there is an issue. ISTA says: Class-H on harness; Class-H stored in control unit; Class-C screening R based on Calc model
• Servo motor says: Actual Angle of Rotation: 6.25°; Actual Calibration Angle: 500° -- not sure what to make of this. It gets cleaned up when successful calibration is achieved?

It's feeling like the transfer case might be bad as there is not enough "back pressure" from the clutch actuation train ( 4 -> 2 -> 1 in pic below.)

I'm interested in any/all ideas to confirm or point away from the t-case clutch pack being trashed. For example:

• Is there a way to read the angle-actual of the actuator while the test is running and see if it travels too far, or current doesn't jump high enough to calibrate?
• Is it listed anywhere what is expected here (e.g. travel between x and y degrees, hit a current >N, consider that the cal point and write it where?)
• etc...

I feel like this could all be in ISTA, but I can't find it.

Big thanks in advance. Definitely want to learn.

[Karle90]

I'm having the same calibration error. On ISTA, I try doing a transfer case repair operation and it can successfully detect the resistor and code it but it fails on calibrating the servo motor. I have a new one coming on Friday to test to see if that's the issue. However, I can hear it spin and I get the same 500 degree calibration angle after it fails. Transfer case status shows not calibrated. What's strange is that it was calibrated before I took the servomotor out to inspect it, so I'm suspecting it might have something to do with it. I'll let you know if I find a fix

[mtntrx]

SOLVED (I think, more road testing required)


I had TWO issues:
1) Transfer case was shot
2) Front wheel sensors were defective or wrong-part

TL;DR recommendations for other

Don't shotgun or parts-canon this. There are steps you really should take.

1. If you are pulling the actuator, do the clutch-cam finger test below. I'd expect NO travel from firm figer pressure.
2. Don't buy cheap wheel sensors. Get the right scan tool and check if yours are working (see direction and speed or get a different tool)

What I learned:

1. A great, quick debug step is to pull the actuator and check what I'm calling the clutch-cam travel by inserting your finger in the hole and checking the travel of "1" in the diagram by pushing on the roller bearing. I'm not sure what the pass/fail criteria should be, but I'll share my data. Bad transfer case: I could push it an inch easily with my finger. With a little help/leverage of a plastic tool it could move it until it bottomed out on the case. New trasfer case: I can't move it AT ALL with my finger.
2. Replacing a transfer case is doable. I referenced a good you-tube video by "Garage Grunt" titled "BMW 335xi Transfer Case Rebuild" I got at 90K case at a junk yard nearby for $200. Some things I'll add to his video: a) Know that the rear drive shaft will move toward the rear of the car once disconnected with a little bit of prying. This is required to move it out of the way. b) an endoscope was invaluable for "seeing" the top bolts. Have a friend hold it in position for you while fishing for the bolts. c) you will be tempted to let the tranny/xfer case hang down to get to those bolts. WATCH the top radiator hose hitting the airbox when the engine tips. That can get torqued and start leaking. Hmmm.. wonder how I know that.
3. Don't buy too cheap wheel sensors. The previous owner probably did a quick you tube "how to fix the trifecta" and tried swapping those. He probalby threw out two great bosch sensors and put in two cheap ones. Cheap wheel speed sensors from amazon might read BACKWARDS. No kidding. Thought I was losing it until I saw another thread here where some saw it too. Then I looked up the reviews on the cheapest set and saw "Don't buy, reading backwards" As a test, I rotated my current (bad) sensors in their holes (180 deg) and hacked in a plastic holder to hold them in place. Worked like a charm... car is happy. That hack is only temporary until I get better ones from FCP.
4. Backwards wheel speed sensors can trigger a steering angle code. My steering code cleared up when I fixed the sensors.
5. After fixing the xfer case, I could make my dash light trifecta go away by running the steering wheel lock to lock 2 times. However, it would instanly return as the car started rolling. Maybe that is another "quick test" that can suggest sensor issues.
6. The speed sensors are interesting. I'll make another post about digging (too deep) into those
7. I read in a few places that the sensors pick up something in the bearings on xDrive cars of this era (instead of a reluctor wheel.). Mine sure looked like a reluctor wheel on the front. I will add pics.

I hope some of this helps. It was a fun learning experience.

[mtntrx]

Here are some pics of the cam-travel. This is the roller bearing from component #1 in the first post. Notice it can move 1 inch pretty easily. I'm assuming this is BAD for two reasons
1) The rotating cam that moves this seems to have less that 3/4" of travel possible.
2) To engage a clutch should required a LOT of force
3) My "new to me" transfer case: this won't budge with a finger. This case works well in my car.

[mtntrx]

As I said above, some folks are saying that some cars use the "bearing" as the encoder for the sensors. I'm uncertain what the setup would look like since the bearing surfaces would need to ride on bearings or races leaving no room for a sensor. I'm probably just not understanding that setup. My 20006 xDrive 325 looks like this in the sensor hole, right/front. It looks like a reluctor ring on the axle OR maybe it is actually carved into the axle metal... not sure.

[stephd203]

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Originally Posted by mtntrx

As I said above, some folks are saying that some cars use the "bearing" as the encoder for the sensors. I'm uncertain what the setup would look like since the bearing surfaces would need to ride on bearings or races leaving no room for a sensor. I'm probably just not understanding that setup. My 20006 xDrive 325 looks like this in the sensor hole, right/front. It looks like a reluctor ring on the axle OR maybe it is actually carved into the axle metal... not sure.

I have the same car...I just replaced my "RELUCTOR" ring. The CV joint has the ring pressed on, then over time, it will get the cancer (rust) and bulge the ring out or cover the ring, or fill in the gaps, etc. I pried and punched the ring off. Cleaned it back to bare metal, and put the new ring on.

https://mega.nz/file/YlpUmAyB#W-mG0x...xExnROoXE4SV38

Having said that, however, my dsc still says that the sensor is not communicating...so I'm still tracking down the faulty wiring or whatever it is....In fact, I have a download from ISTA that shows the Front Right speed sensor going to
the ULF or TCU in the trunk!??? Will be checking that too.

https://mega.nz/file/59JX2QYQ#fng46G...GkNMZbJ47XSSoc

https://mega.nz/file/h04GgZjI#ACPTJF...D5pn8QeU6SSuNQ