[Wh33lr]

Update: My troubles seem so far awa...
I had a bakers' dozen codes. All related to front wheel sensors not designed for XDrive (though listed as such). They were designed for the M3 rear wheel drive.
My decent scan tool (though not Ista level) on live data claimed my front wheels were going in reverse, while the rears were going forward.
Provided the scan images showing the read issue and when corrected.

Attachment 1


Attachment 1


A new to me
2011 E90 328xi N51 GM 6spd GA6-L45R 125K mi w.decent service records.
New'ish tires (no noticeable disparity in tread wear)
The 2 prior owners took care of the basics (oil/tires/brakes). Interior/exterior are pristine.

Dashboard displays:
Red 4X4 ABS error, speed limit/ABS warning & yellow traction control

iDrive system displays the ubiquitous:
1 Braking/chassis stabilization malfunction! and
2 Speed Limit warning

OBD tool originally scanned ~8 DTC codes but now down to 3, then 2 after some driving.

DTCs
Power System:
1. VTG: Oil Wear BMW Fault Code 54C6 - Worn Transfer Case Oil (xDrive Transfer Case Fluid)This fault code is due to work transfer case fluid.

2. Code 55C3 is normally associated with a malfunction in the AWD as well. Typically can be a bad wheel speed or ABS sensor but can also be triggered by the transfer case fault as well. Can also be triggered by the steering angle/position sensor.

3. VTG: AWD Limp-Home Control Activated. No DSC Specified Nominal Torque
ABS (since disappeared)
Safety & Security system (ABS):
DSC: Wheel Speed, Direction-Of-Rotation Detection

Despite the codes, E90 drives zippy and smooth (tested on interstate from 35 to 100mph a handful of times). I do get a momentary 1-second shudder when I cross ~40mph threshold

This shudder never reappears on my continued acceleration twds 100mph.
There is no transmission slippage. I believe this shudder is ABS/Chassis stabiliz... related.
-
What I tried:
360degree steering wheel rotation.
Replaced the frt ABS sensor cables (and gleefully thought issue was resolved).
Initial result:
Both iDrive & Dashboard were clear of codes and warnings from the moment I restarted and tested while still ON the lift.

NOPE! Unfortunately after 1/8th mile on terrafirma, Braking/chassis... and speed limit warnings reappeared on iDrive display
My attempts to clear them with a decent OBD scanner (though not anywhere to the level of Ista) did not remain clear for more than a seconds on the scanner before returning.

Scanning with live data, I monitored front wheel speed on a test drive.
While in DRIVE, the front wheel speeds were not symmetric, with a 1mph variation. While in MANUAL, on the gear selector, the wheel speeds matched identical.
(Brake/chassis malfunction warning still displayed on iDrive and the dashboard still displayed the error).

Where do I go from here?
I intend to change the Transfer Case fluid w TRIAX DTF-1 (IIRC, 1.1pint capacity) which was likely never done before.

Anything else I should look at while changing TC fluid?
No rust.
No suspension linkage damage

[POBEP]

Originally Posted by Wh33lr

TLDNR: Should I change the transfer case fluid? Any thing else while doing so?

A new to me
2011 E90 328xi N51 GM 6spd GA6-L45R 125K mi w.decent service records.
New'ish tires (no noticeable disparity in tread wear)
The 2 prior owners took care of the basics (oil/tires/brakes). Interior/exterior are pristine.

Dashboard displays:
Red 4X4 ABS error, speed limit/ABS warning & yellow traction control

iDrive system displays the ubiquitous:
1 Braking/chassis stabilization malfunction! and
2 Speed Limit warning

OBD tool originally scanned ~8 DTC codes but now down to 3, then 2 after some driving.

DTCs
Power System:
1. VTG: Oil Wear BMW Fault Code 54C6 - Worn Transfer Case Oil (xDrive Transfer Case Fluid)This fault code is due to work transfer case fluid.

2. Code 55C3 is normally associated with a malfunction in the AWD as well. Typically can be a bad wheel speed or ABS sensor but can also be triggered by the transfer case fault as well. Can also be triggered by the steering angle/position sensor.

3. VTG: AWD Limp-Home Control Activated. No DSC Specified Nominal Torque
ABS (since disappeared)
Safety & Security system (ABS):
DSC: Wheel Speed, Direction-Of-Rotation Detection

Despite the codes, E90 drives zippy and smooth (tested on interstate from 35 to 100mph a handful of times). I do get a momentary 1-second shudder when I cross ~40mph threshold

This shudder never reappears on my continued acceleration twds 100mph.
There is no transmission slippage. I believe this shudder is ABS/Chassis stabiliz... related.
-
What I tried:
360degree steering wheel rotation.
Replaced the frt ABS sensor cables (and gleefully thought issue was resolved).
Initial result:
Both iDrive & Dashboard were clear of codes and warnings from the moment I restarted and tested while still ON the lift.

NOPE! Unfortunately after 1/8th mile on terrafirma, Braking/chassis... and speed limit warnings reappeared on iDrive display
My attempts to clear them with a decent OBD scanner (though not anywhere to the level of Ista) did not remain clear for more than a seconds on the scanner before returning.

Scanning with live data, I monitored front wheel speed on a test drive.
While in DRIVE, the front wheel speeds were not symmetric, with a 1mph variation. While in MANUAL, on the gear selector, the wheel speeds matched identical.
(Brake/chassis malfunction warning still displayed on iDrive and the dashboard still displayed the error).

Where do I go from here?
I intend to change the Transfer Case fluid w TRIAX DTF-1 (IIRC, 1.1pint capacity) which was likely never done before.

Anything else I should look at while changing TC fluid?
No rust.
No suspension linkage damage
TIA

1. See if you can monitor all 4 wheel speed sensors.
One of mine had a momentary blips - end up being bad rear right wheel bearing (that I just replaced) - had to do the job twice

2. next option is to check break light switch

3. check/clean all connections/plugs on the TC motor


P.S. VTG: Oil Wear BMW Fault Code 54C6 can only be cleared by running TC oil service job.

[Wh33lr]

POBEP, I DID initially monitor all 4 wheels via OBD Live Data.
IIRC, Rears were not an issue. (they matched up but easy enough to reconfirm).
If rears ARE an issue, I'll update orig thread.

Doubtful bearing is bad. The few times I ran into a failing wheel bearing, I could feel and hear it but worth keeping an open mind (and ear).

For now I'll proceed with the easiest procedure which is a fluid exchange. (research indicates this is a little involved to access the fill hole).

Hopefully not a missing tooth on the plastic Transfer Case Cam Gear (another known issue) though at least a cheap part,
Nor the TC resistor plate (again a reasonably inexpensive part) but a full day for a modestly skilled youtube-mechanic like myself (with access to a friend's lift) to replace it

Appreciate your insight

[POBEP]

Originally Posted by Wh33lr

Doubtful bearing is bad. The few times I ran into a failing wheel bearing, I could feel and hear it but worth keeping an open mind (and ear).

Here is the reason I mention bearing:

I had bad bearing - noisy. obvious.
There were NO speed sensor (or any other) codes.

Next, I had bearing replaced with new, OE part.
The bearing noise went away, but I got codes related to RR speed sensor.

When I monitored speed sensor values with ISTA, they all appear OK at first.
Then I spotted that RR was dropping values.

New bearing had defective ring.

[Wh33lr]

Update: Live Data consistently displays front wheels 1KM/hr slower than rear wheels.
Live data also mentions
Front wheels: Direction-of-Rotation detection is REVERSE (opposite direction of travel)

Lots of info on this reverse-issue due to installing the wrong ABS sensor.
Amz listing claimed part# 34526764858 but I believe (confident) seller is mistaken.

Conjecture: Some BMW "front" ABS sensors are designed specific for rear-wheel drive (lE: M3 and the 328i (w/o the xDrive).

Anyway I held-off on the TC fluid change until after swapping front sensors from a new order arriving next week.
IF this sensor-swap corrects the issue, I may still do the fluid change IF I do not have too much difficulty shifting the TC case alignment to access the drain and fill plugs.

OT: If I had Ista running (I plan to install it on my laptop), I'd have modified my 328i xDrive to RWD, if possible. (I'm aware that function is available via an aftermarket BMW app for >$100)

[Wh33lr]

Update to Update: As suspected, stumbling into the proper ABS Wheel sensor corrected the issue.
The correct sensors relay the correct direction of wheel rotation.


This corrected all of the red and yellow warnings on dashboard:
No 4x4 service light, ABS issues, traction control or other warnings,


Display no longer lists:
Braking/chassis stabilization malfunction & Speed Limit.
No more Scan codes.
All is copacetic.

Sidenote: If you did not have a Scan Tool that could read/monitor wheel direction, not sure how you would realize the issue was the wrong frt sensors.