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-   -   How to diagnose T case vs controller when actuator is good (https://xoutpost.com/bmw-sav-forums/x3-e83-forum/112856-how-diagnose-t-case-vs-controller-when-actuator-good.html)

Natezo 01-20-2021 11:24 AM

How to diagnose T case vs controller when actuator is good
 
So I can confirm good actuator, good wheel speed sensors/signals. Harness to actuator has no visible damage and no codes for steering angle sensor etc.

Nonetheless I have the triad of lights and when I tell my foxwell to run the t case calibration and/or actuator calibration both tests result in “failed”.

I’m trying to confirm how to pin point if the issue is with the t case itself or the controller? Any suggestions?

JP-X3 05-12-2021 11:55 AM

How did you test the wheel speed sensors?
Did you try to disconnect the battery for a more than 10 min?

o2bad455 05-16-2021 09:23 AM

We've got a similar issue with our '08 X3. Dash light triad and rumbling at highway speeds.

Yesterday we replaced the xDrive servomotor actuator on the transfer case, but it seemed to make no difference.

Is there some way to lock the transfer case electrically so I can see if anything's mechanically disconnected (e.g., broken transfer case chain)?

Here's what INPA says in the transmission section (after translation):

E R R O R M E M O R Y --------------------------------------- Date: 16.05.2021 11:52:45 ECU: VGSG83 JobStatus: OKAY Variant: VGSG83 ------------------------------- ------------------------------ RESULT: 2 error in error memory! ------------------------------------------ ------------------- 54C8 54C8 Classifying resistor on the servomotor Error counter: 2 Logistic counter: 40 1. Environment set Mileage 287 160 km input voltage KL30 13.63 volts KL15 status CAN CAN signal OK - KL15 on 0-n KL15 internal KL15. on 0-n motor speed CAN signal OK - ICE on 0-n reset source NO RESET 0-n MKSOLL 0.00 Nm MSperrIstPosLim 0.00 Nm LockError 0.00 1 LockMainState 16.00 1 SGTemp 28.00 degrees C iSM 0.00 Ampere 2. Environment set Mileage 287 160 km input voltage KL30 12.38 volts KL15 status CAN CAN signal OK - KL15 on 0-n KL15 internal KL15. on 0-n motor speed CAN signal OK - ICE off 0-n reset source NO RESET 0-n MKSOLL 0.00 Nm MSperrIstPosLim 0.00 Nm LockError 0.00 1 LockMainState 48.00 1 SGTemp 30.00 degrees C iSM 0.00 Ampere Implausible signal or value Test conditions met. Error currently present and already saved. Error would not cause a warning lamp to light up Error code: 54 C8 68 02 28 8C 37 6D ED 00 00 00 10 0E 00 8C 37 63 E5 00 00 00 30 0F 00 ---------------------- --------------------------------------- 55C4 55C4 CAN_MESSAGE_DSC1 Error counter: 1 Logistic counter: 40 Mileage 287 160 km input voltage KL30 13.63 volts KL15 status CAN CAN signal OK - KL15 on 0-n KL15 internal KL15. on 0-n engine speed CAN signal OK - ICE on 0-n Reset source NO RESET 0-n MKSOLL 0.00 Nm MSperrIstPosLim 0.00 Nm deltaPhiSperreCal -51.00 Grad LockError 0.00 1 LockMainState 16.00 1 DSC1_Fehlersignale DSC1_MK_SOLL 0-n Implausible signal or value Test conditions met. Error does not exist at the moment, but has already been saved. Error would not cause a warning lamp to light up Error code: 55 C4 28 01 28 8C 37 6D ED 00 00 33 00 10 01 00 00 00 00 00 00 00 00 00 00 00 ====================== ========================================

JP-X3 11-17-2021 11:24 AM

Water can get into the cargo area due to clogged sunroof drains. This happened to be back in January 2021 and caused the transfer case to go into failsafe mode (permanent 4wd, hard to steer) and of course the trifecta of ABS, brake and 4x4 lights were all lit.

It took me a while to diagnose this issue because I had recently replaced the transfer case actuator, some front suspension arms, got an alignment and replaced one rear wheel bearing so I was always suspicious about these repairs causing other problems, I was wrong...

I was able to get the transfer case to 2wd by applying 12 volts into the actuator motors' cable at the transfer case controller (VTG ECU) and then disconnected it. Drove the X3 on 2WD for 4 months. I bought the BMW 1.4 scan tool and was not able to diagnose the culprit. Finally I downloaded INPA and got a cable from Ebay. This software has an actuator and VTG ECU test function, there was no communication with the ECU so I bought an used VTG ECU from Ebay for $50, replaced it and voila! it works again.
I took apart the old ECU and to my surprise I found out it's not water tight so water got it, corroded everything and created a short circuit.

o2bad455 09-17-2022 02:59 PM

Quote:

Originally Posted by JP-X3 (Post 1212966)
...
I was able to get the transfer case to 2wd by applying 12 volts into the actuator motors' cable at the transfer case controller (VTG ECU) and then disconnected it.
...
I took apart the old ECU and to my surprise I found out it's not water tight so water got it, corroded everything and created a short circuit.

I think we've now got a similar issue. To which pins did you apply + and - to get it back into 2WD? Same GND as vehicle? Pic?

Recap:

Last year (after my above post in this thread), I'd installed a rebuilt driveshaft (including new U-joints and guibo/doughnut) in our '08 X3 3.0si M-Sport due to one U-joint that was developing some slop (not easily user replaceable on my original due to tack welds, although seems to be user-replaceable on the rebuild due to circlips), and that also cured the rumbling. I eventually cleared the dash light triad with ISTA (due to trouble deciphering online translations of our half-english/half-german version of INPA). So we had properly working AWD/4WD last winter. :)

This summer, the light triad returned with 55c4 as the only code, which I actually suspect is due to a funky speed sensor that I have yet to replace. I'd read somewhere that the same code can be caused by faulty DSC control unit, bad Steering Angle Sensor, and/or failing Speed Sensor. We had noticed occasional momentary dropouts of the speedometer speed for no apparent reason, so that's why I tend to suspect the speed sensor.

Fast-forward to this past week: I was driving home one evening and encountered an epic deluge, including deep standing water (ranging from inches to over a foot) at highway speeds, which did result in some hydroplaning on the half-tread 19" summer tires so I'm sure the AWD kicked in. Although many cars got stuck, and some even kissed each other, the X3 made it home safely (and externally unscathed, albeit considerably cleaner). :)

But as soon as I exited the highway, I noticed shuddering from the inside rear wheel at every slow-speed turn. That is, the left rear shudders on left turns and the right rear shudders on right turns. This led me to conclude that the transfer case is stuck in 4wd.

I let everything dry overnight, but same issue the next day. Took it for a highway drive in clear weather, but no change. Removed actuator plug and blew out with air, but no change. Then dug out my BMW cable, scanned and found codes 55c4, 55c8 and 55c9. According to the mileage snapshots of code occurance, the 55c8 and 55c9 first occured during the deluge drive home, although all three codes now appear immediately after I clear codes and then restart (without even shifting out of Park). I suspect water got into something, but not sure if the VTG, wiring, or actuator itself just yet.

EDIT: The only other post-deluge issue that I noticed is that the exhaust ground strap got torn off. I doubt if that affects anything other than the post-cat O2 sensor, so it's lower on my repair list.

o2bad455 09-18-2022 10:17 PM

After unplugging the smaller 6-pin connector from the VTG control unit, I was abe to duplicate JP-X3's trick to unlock the transfer case clutch pack and transistion from 4WD to 2WD by applying battery positive +12V to the larger red wire. The larger brown wire already had ground, so my connecting that brown wire to battery negative was apparently redundant. It transitioned from 4wd to 2wd so quickly that I wasn't even sure it had done anything until I test drove to confirm success. :)

Just wondering: Could applying a negative voltage to the same red wire re-engage the clutch-pack to switch it back into 4wd?

RocketyMan 09-20-2022 11:48 AM

1 Attachment(s)
Here is the wiring diagram. The actuator gears are plastic...stock. Therefore, I wouldn't be applying voltage at a whim because you can easily strip them--and it's sorta a pain in the butt to replace it because of the heatshield n stuff.

On normal operation, the xcase is only in use under speeds of about 25mph-ish and then in some slip instances. Other than that, it is "off" in normal driving conditions. There is a strategy to help prevent over/under-steer conditions, and I've noticed this myself when going around a sharp corner and hitting the road-"turtles" causing a wheel to slightly slip. Other than that, I wouldn't recommend driving around with the xcase in fully engaged AWD. Also, this will completely wear out the clutches as they will be sacrificed. These xcases are north of $1500 rebuilt.

At usual key-on/off events, the vehicle determines where the end points are on the xcase. I think this is done with calculation of the current draw in correspondence of the actuator.

"
Calibration sequence:
When terminal 15 is OFF, a calibration sequence is performed. During this calibration sequence, a certain angle setting of the VTG actuator motor has a corresponding locking torque assigned. The effects of wear are also taken into account when this is done.

The multi-plate clutch is closed fully and separated once during this calibration sequence. When this happens, the current draw is measured at the respective angle setting of the VTG actuator motor. This determines the beginning and end of the closing movement for the multi-plate clutch. The angle setting is recorded by means of the integral incremental sensor in the VTG actuator motor. These values are stored and are used as data when the car restarts.
"

o2bad455 09-21-2022 09:19 PM

1 Attachment(s)
Quote:

Originally Posted by RocketyMan (Post 1224214)
Here is the wiring diagram. The actuator gears are plastic...stock. Therefore, I wouldn't be applying voltage at a whim because you can easily strip them--and it's sorta a pain in the butt to replace it because of the heatshield n stuff.

On normal operation, the xcase is only in use under speeds of about 25mph-ish and then in some slip instances. Other than that, it is "off" in normal driving conditions. There is a strategy to help prevent over/under-steer conditions, and I've noticed this myself when going around a sharp corner and hitting the road-"turtles" causing a wheel to slightly slip. Other than that, I wouldn't recommend driving around with the xcase in fully engaged AWD. Also, this will completely wear out the clutches as they will be sacrificed. These xcases are north of $1500 rebuilt.

At usual key-on/off events, the vehicle determines where the end points are on the xcase. I think this is done with calculation of the current draw in correspondence of the actuator.

"
Calibration sequence:
When terminal 15 is OFF, a calibration sequence is performed. During this calibration sequence, a certain angle setting of the VTG actuator motor has a corresponding locking torque assigned. The effects of wear are also taken into account when this is done.

The multi-plate clutch is closed fully and separated once during this calibration sequence. When this happens, the current draw is measured at the respective angle setting of the VTG actuator motor. This determines the beginning and end of the closing movement for the multi-plate clutch. The angle setting is recorded by means of the integral incremental sensor in the VTG actuator motor. These values are stored and are used as data when the car restarts.
"

Very interesting, thanks! In addition to this E83 X3 3.0, we also have an E53 X5 4.4, with apparently a slightly larger version of basically the same transfer case. I still think it would be cool to lock and unlock at least the X5 on demand, such as for snow-covered roads at highway speeds (especially if I were to use it for wintertime towing to ice races, etc.). I did buy one metal gear to replace a plastic VTG actuator gear, but never installed it in either SAV.

I've determined with a multi-meter that our X3 apparently got stuck in 4wd (TC clutch plates fully engaged) due at least in part to a burned F80 40A fuse for the VTG control unit. It's an odd-looking fuse (pic attached) that looks more like a semiconductor transistor than a fuse. With battery connected, the voltage on the left side of the fuse measured over 12V, and the voltage on the right side a mere fraction of a volt. I've never dealt with a fuse like this before. Is the discoloration towards the bottom right a sign that it blew, or just a coincidence? Is this a dealer-only item?

Now, why that fuse blew is an open question... Although I'd forgotten, one possibility might be because I'd apparently replaced the X3 VTG control unit with a boneyard X5 VTG control unit over a year ago. It worked great this past winter! I thought I'd recoded, but ISTA just reminded me that the VTG control unit in our X3 is still coded as an "X5" unit, FWIW. Another possibility is simply that something shorted as I drove through that deep water on the highway last week. I suppose the actuator and/or connector probably aren't completely waterproof for immersion versus mere splashing.

EDIT: I did some more digging and learned that this particular type of bolt-down fuse is a slow-blow or time-delay "Midi" fuse.

RocketyMan 09-22-2022 11:49 AM

Not alot of auto-parts stores has parts for our cars. Kind of annoying. But yeah, a midi-fuse sounds about right.


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