C5 X7 no power steering

[wurlycorner]

I haven’t done anything more to it on any fault yet tbh, since fixing the alternator - taking a break from the beating (plus busy sorting out a friends daughters TT).

[the-termin8r]

Hopefully this will be the last time I hijack this thread for battery related nonsense, but I figured I'd put this out there at the expense of what little dignity I have.

I was messing around in the boot today looking at where I can cram the things that used to live in the left cubby (as it turns out I can fit my tyre pump and tow rope in the cavity around the battery). Anyway, I accidentally bumped the negative terminal and saw that it was quite loose. Cue 10 mins of me trying to figure out what the cause was (clamp is perfectly fine) and trying to bodge it with copper tape (with the adhesive stripped) to no avail.

Turns out battery posts are slightly tapered with the narrow end being at the top. It also turns out that I'm a blind cretin and hadn't lowered the terminal as far down the post as possible. The solution was to just unscrew the terminal, push it down so that there's 2-3mm of post sticking up past the terminal and then retighten. A rookie mistake, but at least I've learned something.

[wurlycorner]

During testing for the parasitic draw on mine the other day (will do a new thread for that when I can finally get the pics off my phone!) I discovered that the oem negative terminal on my x7 is an extremely tight fit (externally) in how it fits in the recess on the battery, around the negative post.
It was catching against the plastic housing of the battery at the back, stopping it from being pushed fully down the last few mm onto post without a really good whack and this was stopping it from going tight.

[the-termin8r]

Yeah, I still think I have a couple of mm left on the bottom of mine as well, I just can't get something in there to give it a good enough hit. It's holding for now though, so it's good enough. I'm also on the original negative clamp, it's a far beefier construction than the positive. I don't see it failing at all to be honest.

[wurlycorner]

Still haven't had time to investigate this further (would have this week actually, but of course the weather is now foul!) but... Last week it randomly worked fine once, for about 1 minute after start-up, before going back to 'minimum assist' mode. And yesterday it worked fine again from start-up, for about an hour (and then went back to minimum assist).

[wurlycorner]

Finally got back under it to investigate today.

Firstly, using the Thinkdiag (couldn’t be bothered with the time to run Diagbox) the CSS module had several fault codes stored.

I thought this was the variable steering electro valve (it’s in one of the power steering supply lines) but it’s a three wire component and the wiring schematic shows it’s a two wire component.

It doesn’t show any three-pin components in the circuit, except for the height sensors and rear height switch - so what is this item?
(Incidentally I am not the only person to think that was the valve - see HERE )

So I assume it is instead this, which is on the back of the rack.

I checked the resistance and it measures around 7 Ohms. That’s measured at the sensor itself (unplugged) and both sides of the connector that sits just above the lower suspension arm rear bracket (the one that I thought I had stretched and potentially damaged when I changed the lower arm).

Can anyone please confirm if that is the correct component and if 7 Ohms is ok?

[wurlycorner]

Despite the CSS ECU saying it has no CAN comms and no wake up signal, checking the live data shows it is at least partially working and communicating.

Engine revs and height sensor readings are definitely reading live data, but the steering angle, steering speed and brake release functions didn’t change state.

Does anyone know where the CSS ECU is actually located please? I’d like to check all feeds at the ECU itself and bell out the variable steering valve resistance all the way from the pins there, to see if that shows anything different. Kees posted a pic of the CSS ECU, which if I’m deciphering correctly, suggests it’s in the engine bay, near the fuse box???

After a second code clear it went back to logging on the variable speed valve short/open fault, but no change in what live data it did/didn’t read.

[the-termin8r]

The pile of mush in my skull is struggling to interpret the images in your first post correctly, where is the mystery sensor / connector mounted on the car?

As for the CSS ECU, the PDF I posted a couple of pages ago shows it being somewhere under the bonnet, but the diagram makes it look like it's in the bowels of the car somewhere under the fuse box.

[wurlycorner]

Oh yes, bum - I’d forgotten about that page of the pdf! Thanks. That does seem to confirm the ECU is near the fusebox. Guess I’ll dig that out tomorrow and test from there…
(Nb: neither the wiring schematic, the wiring diagram or the wiring harness drawing show all connectors in the circuit/wiring harness - they all show only a 2pin black connector, at the variable steering valve, but that’s the intermediate connector located by the passenger side suspension arm - the actual connector at the valve, is at the other end of a sub loom from that black connector and is blue in colour.)

For the pics in the previous post (everything is a nightmare to access and photograph on this car because… well it just is because there’s so much crammed in with that big engine!):
The three wire component is passenger side, under the gearbox next to the aluminium front-rear arms on the front subframe.
The two wire component is on the back of the rack, viewed through the gap between the back of the front subframe and the firewall from underneath, and from the back of the drivers side inner wheel arch.
The two wire intermediate black connector is at the rear of the passenger side inner wheel arch.

[wurlycorner]

You see, that connector 7111 is in the same wire harness as the wire from the height sensor, maybe there is something wrong, sometimes because of the movement and some corrosion there's the reason for your problem.

So basically this wiring diagram is a bit deceptive. It makes it look as if the plug for 7111 is on a loom that drops down the firewall in the middle of the car. Instead it drops down to the back of the inner wheel well and is held on a bracket there, above the back of the lower suspension arm. There, it connects to a sub-loom that runs across the top of the steering rack to the valve.

[the-termin8r]

Been digging around the electronics portion of the documentation. Found the PS section and holy cow, it's coloured and interactive! Unfortunately the interactivity doesn't translate to the PDFs.

DT20C power steering (estate).pdf

(438.74 KiB) Downloaded 85 times

DT20C power steering wiring (estate).pdf

(713 KiB) Downloaded 80 times

DT20C power steering CSS ECU location (estate).pdf

(377.87 KiB) Downloaded 72 times

DT20C power steering electrovalve location (estate).pdf

(257.32 KiB) Downloaded 61 times

The electrovalve connector is 7111, the 3 pin listed as 1341 is apparently the DPF differential pressure sensor. I'm not sure if this is the mystery connector from your photos. Also no luck finding resistance or expected measurement info for anything as of yet, but I'll keep searching.

[wurlycorner]

Thanks Rob - yes 7111 shown in that last pdf is the connector in the wheel well I was referring to. That's what connects to a sub-harness that runs across the rack to the valve itself. That's a good image to help anyone in future.

We're still none the wiser about the three pin component then (it's not 1341 - the three pin connector I mentioned is in a completely different location underneath the car and connects directly to the component rather than a sub-harness). The component itself looks like a pressure sensor or switch tbh - but I'm not sure why it would be three pin (suggests 5 or 12v reference and then two signal or control wires)?
Thinking overnight, one of the data streams in the CSS ECU is said to be "Master Cylinder Pressure"... That obviously makes you think brake master cylinder, but I'm not sure why the CSS ECU would care about brake reservoir pressure? I wonder if that's mislabelled and is in fact power steering supply pressure (from that sensor)? Which *would* make sense - but then it's not part of the diagrams, so...?

Either way, I'll ignore that for now and focus on testing from the ECU as planned.

[the-termin8r]

I was thinking it might have something to do with the ESP maybe, so had a look in there, but nothing jumped out. I'll have a look at the mechanical schematics and see if maybe I can work my way back from there to something useful.

[the-termin8r]

Right, I can't for the life of me find anything in the documentation. Nothing online on forums or parts stores either. The only guess I can some up with is a pressure or flow sensor of some kind. Might be worth unplugging it temporarily to see what the car has a panic attack about.

I've fallen down a bizarre rabbit hole with the mechanical documentation. Not relevant to your issue, but apparently the ES9, DT17, 20 and some version of the DV6 run some variation of a belt driven pump, while all the other engines run an electric pump. That might explain why the steering feel between my 2L and 3L differs so noticeably. It also explains the thing I found under the right headlight on the 2L when I pulled the bumper off. Turns out it was the PS pump. On the 3L the 7th sphere appears there. On the 2L I think it's somewhere in the bowels of the car near the bottom of the bulkhead.

[wurlycorner]

Thanks - what does it show on the parts diagram for the power steering pipes?

And yep, I'd twigged from other threads that there was a difference in pumps for power steering - electric/mechanical. I can't think of a good reason why they'd do that though, while the power steering assist itself remains hydraulic!