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?

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.

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).

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)?

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.

Wiring diagram and module location
 

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:

https://www.newtis.info/tisv2/obj/1cLcIor


Wiring diagram:

https://www.newtis.info/tisv2/a/en/e...ic/egp2BNS.svg

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.

Then I am curious what pins x83 pins 1 and 2 are for resistance. What codes did the SVT have prior?

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/

https://www.realoem.com/bmw/images/diag_2snj.png

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)

I think the servotronic can only increase or decrease the power assist within a range, not eliminate it.

Do you mean pins 1 and 2 at the SVT module connector in the glovebox?

I saw it in the linked photo, thanks. I guess testing it probably requires removal. I'll crawl under this weekend to see if I can get hands on it.

In normal operation, that makes sense to me. But what if that valve #5 is completely closed or clogged? I wonder if that valve handles just a control bypass in parallel with the rack or full flow from the pump?

Yes. You should be able to measure some sort of impedance. Then if not, make sure you have continuity on the harness at least. It's just a solenoid like for a transmission. This thing runs on a PWM signal based upon the calculated duty cycle from the SVT module. There is a functional description that explains this that I would have to find. I'd have to figure out if the solenoid is normally open or closed. If open, it would make sense that it would divert all line pressure back to the reservoir and no power assist. Not sure exactly...

So I did some more reading and found the hydraulic architecture for the servotronic PS.

The servo is normally open when no power is supplied to it. Therefore, this would be considered minimum support from the PS pump and divert the majority of assist back to the reservoir (expansion tank).

Supplying the Servotronic valve with power

The Servotronic valve is supplied with power in response to the car's road speed. The power-assisted steering characteristic is memorised in a characteristic curve. The characteristic curve specifies the power based on the car's road speed.
The characteristic curve is written using 16 reference points.

The Servotronic valve is no longer supplied with power when the engine is OFF (over the PT-CAN). Minimum steering force support is set (high road speed) when the Servotronic valve is no longer supplied with power.

Equally, the Servotronic valve is also no longer supplied with power if there is a fault-memory entry.

This leads me to believe there is a fault on the SVT and its effectively turning off the powersteering, aka, no steering force by means of all the DSC issues you mentioned on the previous post.

Where is the pump in that diagram? If steering assist is at minimum (for highway speed) with loss of the servotronic then you would think if that were the problem it wouldn't have cut the assist enough to almost miss the off-ramp?

Haha, OK I see the pump. My mistake.

From what the technical description is saying, it would seem when the servo is off that nearly all pressure is diverted back to the reservoir, thus, making it high effort at the steering wheel.

Sorry for my slow follow-up. With the holidays I haven't had time to even pull the glovebox apart for the multi-meter test just yet. I did read over on the M5board that a bad servotronic valve almost always throws a code. Otherwise, the valve seems easy enough to replace with just removal of the drivers front wheel and a couple of torx bolts to free it from the rack (assuming they don't strip). They also said 4 ohms is good but even a few ohms different is bad, FWIW. So hoping to finally test the valve resistance soon.

Since I've still got no relevant code, though, it does seem at the moment to more likely be an actual pump or rack issue in my case. Not wanting to deal with the rack itself, I can get a 2007 pump (since our X3 is 1/2008 production, but I think the pumps changed in 3/2008) and will probably see if that helps after confirming the correct valve resistance. Hopefully no pump difference for servotronic - I'm assuming just the rack with servotroinic valve would be specified differently with versus without the option. Next I just need to figure out how to get at the pump - hopefully from the top.

If the valve resistance seems okay and the pump replacement doesn't help, then I'll of course swap out the valve, code or no code, before contemplating replacement of the whole rack. R&R of that rack does not look like any fun! More soon...

Progress: The result was 7.7 ohms between pins 1 and 2 (looked like a blue and a green wire, respectively) at the SVT module connector behind the glovebox. Assuming that's the actual resistance at the servotronic valve itself, does anyone know if it's within spec? I do have some manuals (possibly just for E30 and/or E53 rather than E83 - can't remember) but they're elsewhere. I'd read on another forum that 4 ohms was good but 7 ohms was bad, but that might be for a different part number.

Where might I find the correct servotronic valve part number for this 1/2008 E83? FCP (my usual go-to) lists one for just about every other BMW except E83 X3.

Procedure: I scanned for fault codes, then disconnected the battery (is there a way to reopen the hatch without power?), got the glove box apart (much different than write-ups so they must have changed it for LCI - mine used phillips rather than torx), and tested the impedance (technically just resistance) between pins 1 and 2 (looks like a blue and a green wire) at the SVT module connector.

This time fault codes were as follows (still no SVT fault and showed green on the tree page, although there is a DSC fault showing and that showed yellow on the tree page):

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
0000BE KOMBI: Data-filing difference to central light module -1
0000A3 MRS: No message from DSC control unit or message incorrect -1
0000A1 MRS: No message from DSC control unit or message incorrect -1
00003C LM: Number-plate light faulty -1
006E3D DSC: Steering-angle sensor, internal (mileage in km)
00578E EGS: Gearbox oil: wear (mileage in km)

Oh, since the servotronic valve is supposed to be normally open for bypass (minimum assist), could I try applying a fixed voltage to close it (maximum assist) to see if there's any difference (basically just to rule out the pump itself)?

Thanks for the update. Checking the wiring to the servo still is a must, just to rule it out.
I'm sure you checked the powersteering reservoir and made sure it had oil. I'm not sure how else you can check the pump without connecting up pressure gauges on the lines, but if the servo is diverting all fluid back to reservoir, you will wouldn't be able to check pressures properly. When running the vehicle, does the powersteering get warm at all? Maybe the pump did burn up. I'm not seeing any differences on RealOEM for steering pumps with or without servotronic. But there deff seems to be a difference in 5/2008 when the pumps switched over like you mentioned. Good catch.

Looking at the two diff part numbers, the pump castings look the exact same. The only thing i've noticed is perhaps the pump supplier changed from LuK to ixetic. Same company that bought one another and/or joint venture circa 2007? Under Magna Dyne? Hmm..interesting.
P/N
32413428010

32413450590



https://www.realoem.com/bmw/images/diag_3c2e.png

Yeah when disconnecting the battery, I usually leave a rag in the tailgate catch to prevent the catch from locking. At any rate, you can apply power to the jump posts under the hood. HOpefully you have the hood still open, ya?

I still don't like that you cannot see ANY of the wheel speeds. This seems to point to the ABS (DSC) module is NOT reporting on CAN...?

You just reminded me. Let me take a look on my service manual for the e83 to see if there is a value for the servotronic.

It's suppose to be a PWM signal to the solenoid. Applying 12 volts to it would basically set it to 100% duty cycle.



I think these are your problems. The SVT will go into limp mode if it does not see a rational road-speed signal within the first 5 seconds of vehicle start. This seems to be your culprit and coincides with no assist because of no road-speed signals at any wheel.

LoL - I actually tossed a pair of gloves at the hatch latch but heard a telling click while I was dealing with the glovebox and sure enough it had partially latched despite the gloves. I guess they were too thin! Ended up using a jumper pack under the hood just to get the hatch opened, but it made me think there must be a safety relaease somewhere in the trunk area that I should learn about. I could reach the trunk from the back seat, but couldn't get the tilting floor piece out of the way to reconnect the battery without re-opening the hatch.


Wheel speeds or tire pressures? I thought those codes were just for tire pressures... I think I mentioned it earlier but the lack of pressures is only since swapping to the winter tires. I assume they either don't have sensors or perhaps all the batteries are dead. I did have working tire pressures with our original 19" summer tires, which were still on it when this power steering issue first ocurred including for a subsequent highway drive through a blizzard where AWD worked quite well. I'll see if I can find an old pre-PS-failure scan to see if those were ever present before.




Cool, thanks!

Not clear which of "maximum steering force support" or "minimum steering force support" is mnimum assist or maximum assist, respectively, but it sounds like there should be a change in assist 5 seconds after starting if all were well. I don't think I've tried it that quickly, so I'll head back out and try that now...


As for the PS fluid temperature, I'll grab my IR pyrometer and check that too.

Ahh! You're right. The RDC is the TPMS module. Hmmm.... :p:

Well I cannot find ANYWHERE stating what the passing values of the solenoid is in the service manual. -_-

Oh good about the RDC. Thanks for checking about the ohms.


The part number I was curious about earlier was actually for the servotronic solenoid or valve rather than the pump. For some reason I haven't found any part number indicating an application to E83 yet.


In another forum, I'd read something about a "9V battery" test applying power directly to the servotronic solenoid on the steering rack, but peple were hacking their harnesses to do it. Tempted to try 0V vs 9V through the connector while the glovebox is still apart just to see if there's any difference in actual assist, but want to be reasonably sure it won't fry anything before proceeding...

A little 9V battery should be fine. Try it and see if you get any "clicking" when applying it to it. I don't think you need to hack up your harness tho, just a little creativity.

I checked the steering effort in 6 sequential tests turning lock-to-lock (quite the workout) while parked:

1) SVT controller disconnected engine off
2) SVT controller disconnected engine running less than 5 seconds
3) SVT controller disconnected engine running more than 5 seconds
4) SVT controller connected engine off
5) SVT controller connected engine running less than 5 seconds
6) SVT controller connected engine running more than 5 seconds

There was no discernable difference. In every test I had to use both hands and throw some of my weight into it for at least the last half turn of the steering wheel. Oh well, at least it was a good workout. :)

I just realized I probably should have checked/cleared codes after plugging in the SVT, since one of the first 3 tests could have set a code and I can't say for sure that it wouldn't have affected the outcome of tests 4-6.

Might do that and retest 4-6, do a 9V test from the inside connector, and/or run it long enough to measure PS fluid temp changes after I eat.

Thanks for the update. Can you confirm connection to the SVT? What are you using to view the modules? Just ISTA?

I only have ISTA (not ISTA/P yet) working in English. I have INPA too, but it's mostly in German. I've used the old INPA on the X5, but only the newer ISTA on the X3. Since the SVT shows in the ISTA tree view, I believe it's connected. But yeah, if I could translate the German perhaps using INPA might be more definitive.

The PS temp didn't rise very quickly, so I'm beginning to suspect a sheared pump shaft (possibly from the yearly outdoor temperature drop combined with my questionable choice of top up fluid that might well have been thicker when cold).

Our X5 is down for a different issue (rusted rear brake lines where packed into plastic case on arm that apparently catches salt and mud - terrible design IMHO but that's a project for another day). So I need to either get this X3 sorted today or admit defeat for the long weekend (to include too much parallel parking).

Pulled from the local junkyard a greasy PS pump out of a 2007 X3 (that was already missing it's intake mani, making my job unexpectedly easy). Less than $20 CAD including tax, to boot! :) The pump pulley has the same detail as ours, so I think it's the right one. I checked the rack on the donor and did not see any servotronic valve (or I would have grabbed that too). I turned the used pump while removing it and it definitely had good resistance and even moved a little fluid.

I checked Canadian Tire and then Walmart looking for CHF-11S fluid. Neither really had it, although Walmart can ship the Pentosin CHF-11S (to US or Canada) but I didn't have time to wait for that. Called nearest BMW dealer despite 1 hr drive and they were surprisingly out of stock (the parts guy opined that service got more hydraulic PS repairs than usual when the cold snap hit). I remembered using a full synthetic PS fluid in a VW/Audi engine years ago, so called the local VW dealer. VW apparently used the CHF-11S from about 2000-2005, and the local VW dealer had one 1L bottle left among their stock of CHF-202. The CHF-202 is apparently a synthetic blend that can go into any VW (including those with 11S as original fill), while the CHF-11S is full synthetic. VW part number for the full synthetic seems to be G-004-000-M2. It was over twice the price of today's used pump, but at least it gives me a fighting chance.

Collecting my thoughts about getting around the intake manifold and then heading out to swap the pump momentarily (well, as soon as I'm done procrastinating). Fingers crossed!

It's fixed! :D I replaced the pump, the reservoir, and the two lines that connect directly to the reservoir. I was able to do it all just by removing the air filter box and the cables from the alternator (after disconnecting the battery again). The old pump felt okay when I spun it, although I haven't pulled it apart to see if there's anything obvious wrong inside. So the problem was either the pump itself, the non-replaceable filter inside the reservoir, or possibly what seems to be a one-way valve or restrictor in the front line (the one with quick-connect) that comes into the reservoir. :dunno:

Awesome! SOLVED.
 

Great news! So your suspicions of the pump itself was correct. I was thinking that if any pumping were to be happening, that the working fluid would atleast be getting warm.

I'm not too sure HOW important the "green" hydraulic fluid is in comparison to ATF. Some people say that it'll make the seals swell and start to leak. Otherwise, ATF probably would've been fine to at least troubleshoot with. There's really not too many additives in ATF and I doubt there would be that many in 11S neither. A nice VOA of 11S would be great.

I guess a couple take away's from this is that if the SVT communicates on the BUS and has no fault codes, the ABS reports rational road speed, the servotronic in the PS line should be working. I'd be curious now if you were to do you same test of measuring the working fluid temperature if it would be much warmer than last time. :thumbup:

Thanks! To be honest, I'm not sure if my suspicion was right or just wishful thinking. There's no abnormal feel or noise from the old pump, so I was actually worried that I guessed wrong until I buttoned it up and was pleasantly surprised that it was fixed. I really didn't want to have to R&R the rack!

Actually, I think the fluid I'd used for top-up a while back actually was CHF-11S, just in a smaller bottle (355 ml instead of 1 L). It was green too. Anyway, I'm sold on the full-synthetic CHF-11S. I don't like the idea of swollen seals from modern ATF. I've seen too much of that on other cars already.

Agreed. It seemed electronic to me, but apparently only because I'd never had a PS loss with no other symptoms before. The SVT control seemed a likely suspect, especially after discovering the servotronic valve, but it turned out to be a red herring! Go figure...

I'll measure temps again to see if it's much different. Come to think of it, I'd only measured temps just before, in and just after the reservoir this morning becuase those were easily accesible, but probably should have measured just before at and after the pump, possibly from underneath. I believe the PS fluid goes through a cooling loop before it reaches the points where I'd previously measured.

Honestly, the more I think about it, I probably just lucked out today... But I'll take that! :cool:

Well it makes sense if the pump goes. The TIS has quite a big warning about holding the steering wheel in the "locked" position for too long. This is VERY hard on the pump as there is no relief when the steering gear is trying to press all it's pressure on the locks. Once that happens, this causes a no-flow scenario and will then "burn up" the pump. Or in this case, the veins scar the housing, thus, no pressure being able to be produced.

You checked for SVT codes and didn't find anything. There is no "pressure sensor" in the steering--so it makes sense that if the module isn't complaining that the only other probable cause would be the pump since there is no feedback for pressure loss, other than no assist. :thumbup:


Here is a very limited PDS of the 11S:
http://www.pentosin.net/specsheets/Pentosin_CHF_11S.pdf

Then something comparable like this for Valvoline MaxLife ATF:
https://sharena21.springcm.com/Publi...2-ac162d889bd1

Other than both being synthetic, the two have very similar viscosities at temperature. I would expect them to behave the same. Until a VOA of 11S proves otherwise, I'm not convinced it is much different. But ohwell...a topic for a different thread.