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  #1  
Old 12-16-2021, 03:57 PM
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Power Steering Issue

SYMPTOMS: We just encountered the same loss of steering assist (as here: https://xoutpost.com/bmw-sav-forums/...-suddenly.html) without any warnings or other symptoms on our '08 E83 X3 N52 M-Sport (USA Spec). The power steering (PS) simply stopped assisting after stopping for gas on the way into a congested city, which almost made us overshoot an exit ramp and then made tight curb-side parking unexpectedly challenging. There is no noticeable fluid movement in the reservoir with the engine running, but the belt's good, pulley's not wobbling, no noises or PS leaks.

CONTROLLER?: I thought it might be a steering controller fuse, but fuses 66 and 69 both seem to be fine. Is there any possibility that this could be a controller issue? If I understand correctly, although it seems not to be well documented, the steering controller supposedly actively adjusts the amount of assist. Anyone know if it adjusts to zero assist under any circumstances, even if just in a failure mode? I couldn't find any relevant fault codes using INPA, but just got ISTA working again (under an updated VBox Win10 VM, FWIW) and it just reported code "0000A1", description "MRS: No message from DSC control unit or message incorrect", and mileage "-1". Could that code be relevant? The only two other codes (for gearbox oil wear and a number-plate light) both showed actual mileages.

RESERVOIR?: I read that the PS reservoir has a non-removable filter. If it got plugged somehow, could that cause the issue? Has anyone successfully removed the internal reservior filter (I'd add an external one, of course)?

PUMP?: If not the controller or reservoir filter, I guess we'll be ordering a new PS pump. But I've truly never had a hydraulic PS failure anything like this before. It makes me wonder: Are these PS pumps' impellers made of plastic? If so, is there a metal impeller version or upgrade available? Our vehicle assembly date per the door-jamb VIN sticker is January 2008, although ISTA just identiifed it as September 2007 (I presume retrieved from a control unit, but no idea which). It looks like there were several different pump versions in a 2-3 year period, so I guess I ought to at least pull the lower shield off to take a picture before ordering.

FLUID?: I will say that the fluid had been right at the min mark when cold and about halfway to max mark when hot since we got the X3 a couple of years ago. When on a long trip this past summer, I decided to top it off to full when hot using Prestone European Power Steering Fluid, which listed "BMW" on the front label and "CHF-11S" in the fine print. After pump replacement, exactly which readily available fluids should we use or avoid?
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1994 318i (E30-LCI) race car - sold

Last edited by o2bad455; 12-16-2021 at 04:17 PM.
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  #2  
Old 12-16-2021, 05:27 PM
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I would say more likely that you have blown a seal in the steering rack. It can be a bit tricky to determine which is at fault so you might be better off taking it to a shop.
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  #3  
Old 12-16-2021, 06:05 PM
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Quote:
Originally Posted by o2bad455 View Post
SYMPTOMS: We just encountered the same loss of steering assist (as here: https://xoutpost.com/bmw-sav-forums/...-suddenly.html) without any warnings or other symptoms on our '08 E83 X3 N52 M-Sport (USA Spec). The power steering (PS) simply stopped assisting after stopping for gas on the way into a congested city, which almost made us overshoot an exit ramp and then made tight curb-side parking unexpectedly challenging. There is no noticeable fluid movement in the reservoir with the engine running, but the belt's good, pulley's not wobbling, no noises or PS leaks.

CONTROLLER?: I thought it might be a steering controller fuse, but fuses 66 and 69 both seem to be fine. Is there any possibility that this could be a controller issue? If I understand correctly, although it seems not to be well documented, the steering controller supposedly actively adjusts the amount of assist. Anyone know if it adjusts to zero assist under any circumstances, even if just in a failure mode? I couldn't find any relevant fault codes using INPA, but just got ISTA working again (under an updated VBox Win10 VM, FWIW) and it just reported code "0000A1", description "MRS: No message from DSC control unit or message incorrect", and mileage "-1". Could that code be relevant? The only two other codes (for gearbox oil wear and a number-plate light) both showed actual mileages.

RESERVOIR?: I read that the PS reservoir has a non-removable filter. If it got plugged somehow, could that cause the issue? Has anyone successfully removed the internal reservior filter (I'd add an external one, of course)?

PUMP?: If not the controller or reservoir filter, I guess we'll be ordering a new PS pump. But I've truly never had a hydraulic PS failure anything like this before. It makes me wonder: Are these PS pumps' impellers made of plastic? If so, is there a metal impeller version or upgrade available? Our vehicle assembly date per the door-jamb VIN sticker is January 2008, although ISTA just identiifed it as September 2007 (I presume retrieved from a control unit, but no idea which). It looks like there were several different pump versions in a 2-3 year period, so I guess I ought to at least pull the lower shield off to take a picture before ordering.

FLUID?: I will say that the fluid had been right at the min mark when cold and about halfway to max mark when hot since we got the X3 a couple of years ago. When on a long trip this past summer, I decided to top it off to full when hot using Prestone European Power Steering Fluid, which listed "BMW" on the front label and "CHF-11S" in the fine print. After pump replacement, exactly which readily available fluids should we use or avoid?
Alright...cool. Lets see if we can narrow down your issue here. I highly doubt adding in different hydraulic fluid would absolutely kill something.

Do you know how to use mdecoder? Can you check on your vin if you have option code "216" assigned? This will tell us if you have servotronic steering.

You might already know this but, here's what NEWTIS says:


New: In E83 the Servotronic is integrated in its own control unit.

The Servotronic is available as special equipment (option 216).
Brief description of components
The following control units are involved in the Servotronic:

Servotronic control unit (SVT)

The SVT control unit specifies the nominal values for controlling the Servotronic valve (hydraulic pressure). The SVT control unit is connected to the PT-CAN (powertrain CAN) and K-Bus (body bus).
[more ...]

DSC control unit (Dynamic Stability Control)

The DSC control unit delivers the car's road speed signal. The DSC control unit and SVT control unit are connected by the PT-CAN.

DME or DDE (Digital Engine Electronics or Digital Diesel Electronics DDE)

The Servotronic receives the signal of whether the engine is running from the DME or DDE over the PT-CAN. The Servotronic only activates the Servotronic valve when the engine is running.

Instrument cluster (KOMBI)

The instrument cluster delivers the terminal status (e.g. terminal 15 ON) and the kilometer reading.


If you indeed have the option on your car, the module needs to be on PTCAN in order to determine road speed to adjust the valve. This would make sense if your DSC is not "on" for some reason.

Do you have the "trifecta" lights on your dash? 4x4, amber-BRAKE, etc....?
This might be the case if the MRS module is complaining about not seeing the DSC.

Here's some miscellaneous info:

SBT Enclosure E83 General information on Servotronic, En
Important. Do not hold the steering wheel at the limit stop for a long time.
The power-steering pump does not have a limit stop mechanism. The power-steering pump may become damaged if the steering wheel is held at the limit stop for a long time (1 minute and longer).
Note: different power-steering pump for different engine variants
Different power-steering pumps are used for different engine variants. For petrol engines the equalizing tank is installed separately from the power-steering pump. For diesel engines the equalizing tank is flange-mounted on the power-steering pump.
Note: cooling fins instead of cooling coil
For diesel engines the power-steering cooler has cooling fins instead of only one cooling coil (introduction also planned for petrol engines).
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  #4  
Old 12-16-2021, 06:06 PM
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Thanks 80stech! Oops, I hadn't considered the possibility of the rack... With a new pump well over $800 w/ tax, that sounds like really good advice, thanks! BTW, it looks like ours has the pre-3/2008 version, although the post-3/2008 version is only half the price. Anyone know if the later one can be used instead? Did they change connectors or something, or is it a completely different animal (possibly related to the mysterious active steering control)?
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Last edited by o2bad455; 12-16-2021 at 06:19 PM.
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  #5  
Old 12-16-2021, 06:19 PM
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Thanks RocketyMan! I didn't know most of that. Yes, mdecoder does report "S216 Hydro steering-servotronic"

EDIT: I have had the trifecta of lights in the past, although not currently. A local BMW specialist had indicated that it looked like an intermittently malfunctioning DSC (from memory), although he said it's usually one of a few other issues but ruled those out in my case. I'd picked up a used controller (still attached to the back of the donor ABS unit), but was waiting to put it in (and then have it recoded) until the next time the intake manifold has to come off. In the meantime, the trifecta hasn't been around lately and AWD had been working quite well in two recent snow storms, the first on 19" summer tires before the PS failed, and the second on 17" winter tires after the PS failed.
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Last edited by o2bad455; 12-16-2021 at 06:37 PM.
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  #6  
Old 12-16-2021, 06:35 PM
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Wiring diagram and module location

Quote:
Originally Posted by o2bad455 View Post
Thanks RocketyMan! I didn't know most of that. Yes, mdecoder does report "S216 Hydro steering-servotronic"
Okay...awesome. Now we know your vehicle is spec'd with servotronic!

Next I can give you the wiring diagram for this. You said you have ISTA, right?

Can you go to your architecture tab and see if the servotronic reports on the network? What about the DSC? The servotronic should report as "SVT."

The module is located behind the glove box...here:




Wiring diagram:

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Old 12-16-2021, 06:54 PM
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Both the DSC and the SVT are reporting in the "tree" view. I'd cleared codes earlier due to what I thought was a tire pressure calibration issue (before realizing it was just that the 17" wheels from a base model lack pressure sensors unlike our original 19"). I haven't driven it since clearing codes, but the DSC and the SVT modules currently both report as green.
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Old 12-16-2021, 08:23 PM
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Then I am curious what pins x83 pins 1 and 2 are for resistance. What codes did the SVT have prior?
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Old 12-16-2021, 08:56 PM
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We need to figure out if its the servo... #5
Could also be dirty, or clogged perhaps...stock open/closed.

There is a tiny little filter in it.
You can see it here: https://www.turnermotorsport.com/p-5...uine-bmw-part/

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Old 12-16-2021, 09:19 PM
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The SVT itself has never reported any codes per ISTA, AFAIK. Just back from a spirited 20 minute drive with several on/off cycles. It's showing 3 yellow dash lights for tires, lights, and check engine. I do have codes but none attributed to SVT:

Code Description Mileage (perhaps in kms)

000004 LWS: Slider fault (adjustment operation) -1

000004 RDC: Wheel detection not possible -1

00002E RDC: Wheel electronics, front left: no reception -1

000031 RDC: Wheel electronics, front right: no reception -1

000034 RDC: Wheel electronics, rear left: no reception -1

000037 RDC: Wheel electronics, rear right: no reception -1

0000A1 MRS: No message from DSC control unit or message incorrect -1

00003C LM: Number-plate light faulty -1

006E3E DSC: Steering-angle-sensor adjustment required (redacted)

00578E EGS: Gearbox oil: wear (redacted)

002A82 DME: VANOS intake (redacted)
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