C5 X7 no power steering

[wurlycorner]

Hi all

On my 2011 X7 3.0 V6 HDi tourer.

Properly scratching my head here… I’ve just finished changing the following:
- Offside outer track rod end
- Nearside lower suspension arm
- Nearside FRIP joint
That’s it, nothing else.
Just taken the car out for a spin, suspension working fine, steering etc all working fine, no noises etc but I have basically no power steering.

I’ve put it back on stands, pulled the steering from either wheel manually and it feels fine, nothing binding, no odd noises etc.

I’ve run the engine with it on stands and there is no change in how easy the steering wheel is to turn with engine on, or off.

I don’t understand this - I’ve not touched the rack, pump/any of the hydraulic circuit.

The only thing I can think of that may be related to the power steering that I disturbed is the two electrical connectors that mount on the bracket bolted to the nearside lower suspension arm rear bracket - is one of them related to a sensor/variable assistance control for the rack? However I didn’t disconnect them, I simply unbolted the bracket from the old arm mount (complete) and bolted back onto the new one. I’ve looked and they’re still connected fine, no obvious signs of distress or damage.

I’ve done a lexia diag and I can’t see any code relating to power steering (not sure which ECU it would be in tbh - doesn’t have the power steering ECU of course and when I looked in the Engine ECU, Suspension ECU, variable comfort ECU, BSI… I couldn’t see any live data values relating to power steering???

Any data pids that I could see in those ECUs for engine speed and vehicle speed, all seemed to work just fine.

This is absolutely nuts.

Anyone any ideas please?

[wurlycorner]

For what it’s worth, these are the faults stored in the suspension ECU

[RichardW]

There's a permanent fault for vehicle speed, assuming this has variable PAS I imagine that's what causing it. Will it clear? Is the ABS light on? Possibly the wires you disturbed are speed sensor related, and the data is now lost somehow?

[wurlycorner]

No warning lights on dash.
The fault clears but comes back if I then rescan it I believe.
All the vehicle speed live data that I could see in those ECUs reads fine when I watch it and drive the car backwards/forwards.
I think Marc previously said all those faults come up when you scan on this model, regardless? (I’ll have to see if I can find the post…)

Nb: I would have also disturbed the wiring to the Nearside ABS sensor when I unbolted the brake disc heat shield - but I didn’t unbolt the sensor, unplug it, or remove the hub or the driveshaft from the hub while changing the lower arm/FRIP joint (everything stayed connected) plus there is no ABS fault showing, so I don’t see it can be that either.

[Kees]

I think you should follow the airbleeding procedure.
Put the car in the highest position and turn the steering wheel from left to right, but not hold against the stop, even better turn around the other way before this point.
Then put the car lowest and do the same.
I hope this solves the problem.

[wurlycorner]

Yes, I guess even though the suspension is working fine (has done full low - full high and back to normal etc) and the steering hydraulic circuit hasn’t been disturbed, I guess it is possible that somehow through having the wheels dangling etc it has still got air locked???

I shall try
(frustratingly as it is back on stands in disgrace at the moment, this will have to wait till at least Friday, as I’m out all day tomorrow till very late!)

Thanks

[wurlycorner]

Marc confirmed in this post that it’s the variable comfort ECU that controls the variable power steering on this model.

[Kees]

It's not right to let the wheels dangling, without first put the car in the highest position, the It's better to put the lower and depressed the system with the diagbox/lexia and disconnect the battery.
Also what I say about airbleeding, the car must stand on the ground.

[wurlycorner]

Yep the suspension was full high to full low before wheels dangling etc. and the suspension full low/high etc was with it on the ground.
It’s just beck on stands because I put it back there to recheck there was nothing binding/amiss etc.
(I don’t disconnect the battery though. Never have/do unless I’m working on something that would otherwise be permanent live/battery itself etc.)

[Kees]

A few days ago I explained an other forum user this about what possible can go wrong and the reason why.


Partial, you're right. But even when the control of the LDS fluid level is done correctly, and there is not to much of LDS fluid in the tank it's still possible, that the tank burst when they jack him up the wrong way, the reason is, that when the wheels hang loose in the air, the electronics system think, the car is standing to high and therefore opens the return valves in the BHI, and let the fluid runs freely in the tank.
Now if you than put the car down, the struts goes suddenly from the highest position in to the lowest.
The remaining fluid goes under pressure back to the thanks and if the cap is not twisted loose the chance will be, the tank burst.
By the way, you can prevent this to happen, by just disconnecting the battery.
This how I do it sometimes without put the car in the highest position, because the valves I'm talking about before stay close, because there's no power to open them.
Greetings.
Kees.

[wurlycorner]

Update: ridiculously (embarrassingly) current suspicion is that this might just be the LDS Fluid is low. Obviously I didn’t imagine it could be that, because the power steering was working absolutely fine until I did the work above - none of which disturbed any of the hydraulic system and there’s no leak suddenly appeared either. The suspension is working fine and no warning light etc. but it is low when I check, so here’s hoping that’s what it is and it’s somehow just caused a weird airlock in the steering system. We shall see.

Oh and obviously I have none in stock at home and there’s nowhere nearby open this evening that had it either, so I can’t resolve that of course… #-)

It is rather frustrating how difficult LDS has always been to find in stock anywhere locally, compared to LHM.

[wurlycorner]

It was a litre low (still staggered that the suspension worked absolutely fine and no warning messages, given that?).
However: unfortunately this made absolutely no difference.
So I’m back at square one. Unable to understand how on earth this intact hydraulic power steering system, that’s not leaking, where the pump is running and was not disturbed… can possibly not be working.
Time to get diagbox out and delve into the CSS ECU again.

[wurlycorner]

Finally the car acknowledges it has a problem…
Quite surprised that loss of power steering isn’t ‘serious’ enough for it to put a fault light on the dash, but hey-ho.

[Kees]

It's a bit strange, about the stepper motors, because this belong to the C6 with amvar system.

[wurlycorner]

Yes, I don’t understand the stepper motor references.
I can’t see anything on this forum for C1132 (code set criteria, causes, fault finding etc) or anything relating to the steering system in general (aside from the rack of course!).
Unless someone has access to that information please, I’ll have a look on c6 owners and see if there is anything helpful there.