Hydractive strangeness

[aerodynamica]

I was out in Auld Katy yesterday for a trip up north to see some lovely turning leaves in the forests and the car performed very well on the 150 mile round trip. Upon dropping off my friend in Stirling I noticed the suspension had stuck in hard mode and remained so even after the door was opened and closed. I set off anyway and the normal service resumed with the switching to stiff springs as and when. Got back parked up for the night. I don't drive to work so the car stood all day today but took the Xant to the supermarket 2 miles away this evening and this time I felt the suspension was actually sticking in SOFT mode. It was most noticiable pulling away from lights where the accelerator pedal movement didn't seem to be making the springing stiffen for those seconds after you pull away. It continued to do this whether pressing or lifting the accelerator. I tuned the radio to LW and sure enough the electrovalves could be heard singing their alien harmony constantly - no movement of the pedal or twitch of the steering made any interruption! It was stuck in soft mode for sure.

I recall hearing something on here about the tail gate switch failing and causing it to stay in soft so I tested this at the shops and it seemed to be working: ignition off, doors locked and after the wait the 'click' of the electrovalves was heard and bouncing the rear and front revealed it was firm. Opened the door and - click - the suspension was soft front and back.

Checked the tail gate's effect and sure as, it was allowing it to switch to stiff after closing.

Returned after 10 minutes and started up and found it drove as before, in perma soft mode. so what's going on? If it's in soft mode then the ECU is telling it to be in soft mode as faulted out system defaults to stiff mode AFAIK. I drove over a 1/4 mile street of speed humps on the return and again the soft mode was constant (and for this, very good) so the body movement sensor similarly was not giving a signal. Perma soft all the way home.

To make matters confused, by the time I got home it seemed to change to stiff at the front and perma soft at the rear.. Soft at the front returned as I was putting it into the lock up (i.e stop, door open, closed, drive etc). It has done the occasional stiff at front before but not sure if this is related to the perma soft phenomenon.

Only other detail is the speedometer has stopped (on Saturday before any strange hydractive stuff) likely due to the drive cable maybe not fully engaging after I changed the dashboard bulbs the previous weekend. Couldn't be related? because the speed sensor is surely at the gearbox end of the drive cable.

I am a bit stuck on where to start. On my last XM, hydravtive I, the speed sensor was not getting its signal to the ECU and the ECU thought the car was stationary. It stayed soft but reacted to the accelerator pedal sensor switching to stiff and back. It did so for about a minute of driving where the ECU faulted to stiff mode due to repeat pedal sensor inputs but no speed info. Only stopping and opening the door or restarting would reset it (it seems the ECU disregards all inputs except the pedal at stationary ) I found on the XM that by disconnecting the pedal sensor until the speed sensor fault was resolved that it remained on permanent soft mode as it thought the car was stationary and then there was no pedal input. But the xantia surely IS getting pedal input as that's still connected.. what's happened

[xantia_v6]

I would recommend getting the car connected to a Lexia to check the hydractive input parameters, especially the speed sensor input.

[Mandrake]

Welcome to the world of Hydractive 2 - never twice the same behaviour over the same piece of road.

I think sticking in the hard mode intermittently (either mechanically, or electrically) is pretty common at the age they are now. Apart from the electrovalve problems like open circuit diode, dry joint on the coil, or pitted needle valve, you also have low system pressure and sticking shuttle valve in the main block as possible culprits!

I have never heard of sticking in the soft mode though. Are you sure that the electrovalve really was staying energised when it shouldn't ? If it was only a lack of response to the throttle then the throttle position sensor could be faulty - but sharp steering or hard braking (on an S1) should still make it go to hard mode. It might be possible to squirt some contact cleaner into the potentiometer if it is just a bit oxidised.

If even sharp steering doesn't trigger hard mode then a faulty speed sensor as suggested is more likely. There is a coherency test done with the speed sensor - if the ECU sees repeated use of the accelerator pedal and brake pedal with no indicated road speed it will eventually drop into limp mode which will put it into hard mode however turning the key off and on will clear this and cause it to go into soft again for a while.

It won't be tail light switch or door switch to blame - they only do anything when stationary, above a certain road speed (about 25km/hr I think) they are ignored.

[CitroJim]

I would recommend getting the car connected to a Lexia to check the hydractive input parameters, especially the speed sensor input.

And with a passenger's assistance, or you as passenger with trusted driver, you can observe what the electronic side of the Hydractive system is doing whilst on the move...

Welcome to the world of Hydractive 2 - never twice the same behaviour over the same piece of road.

Many a true word spoken in jest Simon!

But yes, as you say. A good first check is to tee in a pressure gauge just beyond the pressure regulator and see what the system pressure is. I does not need to be far down on an S1 to start giving odd Hydractive problems...

[white exec]

It's also very confusimg if the front and rear of the car's suspension is behaving differently. Using LW on the radio to monitor suspension ECU 1kHz output could also only tell part of the story, because the ECU, iirc, only has one pulsed output generator, which is split through the two output semiconductors to feed the two EVs. So one EV could be working, and the other not, even if you can 'hear' the signal. Or one output channel could be intermittent, either on or off.

Have you fitted a couple of dash LEDs, wired into the ECU plug, so the output to each EV can be separately monitored? Especially useful while driving. (Theoretically better to wire them into the system at the EV end at the two-pin connectors, but this is probably overkill, (a) because access and wiring route is awkward, and (b) suspension ECU automatically checks wiring and EV solenoid for continuity and resistance, and would report a fault.)

Sticking in soft mode is very unusual, as Simon says. Can only be physical sticking of the hydractive valve (dirt?) or a rogue electrical signal being fed to it/them, or sensor fault - hence the real need for the individual LEDs, plus a Lexia check.

Apart from all the checks above, the new-type hydractive valves (and no, I'm not on commission!) would swat any slightly low hydraulic pressure issues, but that isn't the cause of getting stuck in Soft.

[CitroJim]

Good thought on fitting monitor LEDs to the electrovalves Chris

It was all the rage once to do that, especially on Activas, but seems to have fallen out of fashion recently. I'd all but forgotten about it until you jogged my memory..

That is as good as riding as a passenger and cradling a Lexia on your lap...

[aerodynamica]

Hi all, just a quick reply for now: it's definitely not mechanically sticking as I hear the whine of the EVs with the engine off. I've not yet fitted leds for the outputs but I did do this on my last XM (1 LED s it was hydr1 ) but yes I'll need to find a man with a lexia. It's possible that Ronnie at Graham Harper's in Glasgow has one - anyone from the Scottish contingent know? I also have not yet fitted the diodes to the system as I intended to fit them closer to the EVs than the ecrofting kit does.This is based on advice from one of the electronics engineers at work tho maybe not that essential for this application. Anwar I'll get back to you all later! Thanks for the replies so far!

[aerodynamica]

Been in touch, neither he nor Citroen services in rutherglen seem to have a machine any more.

I think I'll have a look at the possible simple stuff first like the speed sensor and its wiring etc

[CitroJim]

Do you have any fellow FCF members who might be willing to do the necessary near you with a Lexia Graeme?

In this application it does not matter where the diodes go... It's only an issue in high-speed switching applications and this is not one of them even though it seems quick to us...

[aerodynamica]

Ah I see Jim. Well that's good because I was wondering how to water proof any retro fitted bits near the EVs.

Not sure any members near me have a lexia?

[myglaren]

David Hallworth is in Glasgow and may be willing to spare some time with you
Map.

[aerodynamica]

Thanks (forgot about the Lexia map) and actually RichardW is closer to where I work on the car. Cheers all

Just thinking there, the speed sensor is also unlikely to be faulted because surely even if it gave no signal the pedal sensor would still work since it works from stationary. Who knows, probably not have the car out until Friday at the earliest.

[white exec]

The LEDs are the starting point; they eliminate lots of guesswork.

I found a 30mA LED with 120R* in series worked well in practice, and clearly shows the 12v 0.5sec pull-in, followed by the '3v'/1kHz hold-in.
A couple of flat-top 3mm round LEDs fit easily into the dash (just drill two 3mm holes, and push in), and include a switch to kill them when not required. Grounding the LEDs at the dash saves a cable from the engine compartment. When not illuminated, the flat-top LEDs merge with the dash surface, and are almost unnoticeable.

* Not quite a calculated value, but provides good balance of output between initial 12v burst and hold-in.

[aerodynamica]

Thanks Chris, I'll likely add the LEDs. I'm also looking into reactivating the redundant lamp in the dashboard for the Hydractive. As you know the XM has the yellow lamp in the dashboard that lights up to test much like an ABS light and it flashes to signify a fault etc. The Xantia apparently had this too for the first months of production and it was then deleted. The lamp remains in the dashboard but isn't connected. I decided to throw a new bulb in that lamp the other week to see if in fact the wiring was still there but that perhaps they only removed the bulb in production but of course, it was a bit more complex than that! The bulb didn't light when fitted. I was just looking at some Hydractive II training manual that includes description of the lamp and I believe it gets 12v at the dashboard fitting and that it is earthed through the connection at the ECU (pin 10 on the white plug) In theory all I need is a wire from the vacant point on the dashboard multi plug to pin 10 on the hydractive multi plug (and the bulb of course) and I should get the yellow lamp back in the dash. It will then alert to a detected fault by flashing when the ignition is turned on or stay lit if the ECU has an internal fault. I'm still unsure why they deleted this lamp. A suggestion by Jim in another thread was that the 'sport' button on the middle console has a light to show when it is in sport mode and that this replaced the function of a dashboard light but I wonder, because this switch has no 'flashing' function or 'test' 3 second light up on ignition and so isn't attempting to show any test kind of information. Does the series 2 XM still have the hydractive test lamp?

[aerodynamica]

Welcome to the world of Hydractive 2 - never twice the same behaviour over the same piece of road.

I think sticking in the hard mode intermittently (either mechanically, or electrically) is pretty common at the age they are now. Apart from the electrovalve problems like open circuit diode, dry joint on the coil, or pitted needle valve, you also have low system pressure and sticking shuttle valve in the main block as possible culprits!

I have never heard of sticking in the soft mode though. Are you sure that the electrovalve really was staying energised when it shouldn't ? If it was only a lack of response to the throttle then the throttle position sensor could be faulty - but sharp steering or hard braking (on an S1) should still make it go to hard mode. It might be possible to squirt some contact cleaner into the potentiometer if it is just a bit oxidised.

If even sharp steering doesn't trigger hard mode then a faulty speed sensor as suggested is more likely. There is a coherency test done with the speed sensor - if the ECU sees repeated use of the accelerator pedal and brake pedal with no indicated road speed it will eventually drop into limp mode which will put it into hard mode however turning the key off and on will clear this and cause it to go into soft again for a while.

It won't be tail light switch or door switch to blame - they only do anything when stationary, above a certain road speed (about 25km/hr I think) they are ignored.

Ha thanks Simon, there was me thinking I'd have less trouble with HII than the HI from my last XM the HII on my previous Xm never seemed to give any problems though

As for the pedal sensor - I actually have a spare one and a spare speed sensor (though it's an XM in-line with speedo cable one so might not be the same) so these are swap able as a quick check.

It's strange too, talking on the other thread about Hydractive 2 evolution to those late type firmness regulators, despite being an early series 1 with the old type regulators, the suspension does still switch to soft with the doors open after a good 15-25 minute stand suggesting to me that the reserve pressure in the accumulator remains high enough to still activate them after this time. Still going to do the modification to the modified regulators though