Citroen XM Forum

Check the part numbers on the hydroactive spheres in case corner spheres have been fitted by mistake.

Dieselman wrote: Does the lamp come on when you manually select Sport mode?

Where are you and is that the car recently on sale in Derby, if so it was a trader so insist they fix it under warrantee.

No lamp at all, and yes it is the Derby area car.

Richard2cv wrote:Haven't seen a signal generator since I was at college. what does it do again?
It looks a bit like the stereo in a nissan pao.
Also I really like the colour of that car.

It produces various waveforms and in this case it is making a square wave to emulate to speedo sensor so I could test the cruise control statically.

Thanks for all your replies, went to citroen today and bought a cruise solonoid (1628 L9) £17.45 and a exterior temp sensor (6445 F9) £26.14! ouch

Welcome to the world of XM ownership Cromptons

I'm still a newbie and it took me a while to really embrace the thing.. I was always (still am) a committed Xantia owner and came very late to the world of XMs. They take a bit of getting used to and then they really win you over big-time...

Interested in your fix and testing of the cruise control. I had a problem on mine which turned out to be a couple of duff transistors and a diode in the ECU.

I checked my speed sensor by taking a little battery operated oscilloscope for a ride on the passenger set with a wire leading from the ECU connector to the 'scope via the door rubber...

Thanks Jim

Took the xm for a 100 mile rtn cruise down the M1 on Saturday. Drives quite nice to be honest!

Started having a serious look at the suspension issue (in hard mode, no sport light).
So reconnected the electrovalve feed wires to pins 1 and 2 on the ecu (after being connected to a +12v supply). they still measure 4 ohms each so hopefully not blown.
Found there was no supply to pins 1 and 2 on the black plug, this was fuse 34 missing (sure it should be fuse 7 for hyractive 2?).
Checked all the earths and the various easy inputs to the ecu, only issue I can see so far is the Braking sensor signal is always earthed, does this use sensor on the pedal or another one?

Is there a list of faults which causes the ecu not to to pass it's self test? Also got a spare ecu which makes no difference.

Going to fit the electrovalve diodes next.

Anyone in Derbyshire have a lexia?

A new issue is that it sometimes doesn't go into park, it car will roll forward etc.

That's interesting - another XM that's had it's wires cut. Seen it a few times now

If there's not one on here already I'll do you a guide but for now this Activa buyers guideon the FCF is good to basically test the Hydractive suspension - just ignore the Activa-specific bits..

Also, have a good read of the Citroen Technical Guide. It tells you how the suspension works in exquisite detail.

You clearly know your electronics so that'll be no worries.

A very common fault on the electrovalves is the back emf suppression diodes going open circuit. It's very easy to pop an outboard diode such as a 1N4004 across each valve coil.

Also, if you have a 'scope you can pop that across the electrovalves and see a nice 1KHz almost 50:50 squarewave when in soft mode. A duff diode will show considerable ringing on the waveform.

We can get to that later after you've done some basic tests.

iirc, the Sport light should illuminate whenever selected, even if the ECU is faulty, as the switch shunts the feed straight to Gnd. It would be worth measuring the feed to the switch and possibly there is no bulb in the holder as it is always in sport, so been removed.

My understanding of Hydractive 11 is that:-

In a moving car the Sport light should illuminate only while the suspension ECU selects the firm state.

At ignition switch on the warning light has three separate states.

Illuminates for 3 seconds - ECU operation tested with no stored fault codes found.

Flashes for 3 seconds - ECU operation tested and stored fault codes found.
(note that the ECU also flashes the light for 3 seconds in a moving car at the point when a new fault is confirmed and stored in the ECU).

Warning light does not illuminate - Bulb or ECU defective.

John

xmexclusive wrote:
Warning light does not illuminate - Bulb or ECU defective.

That's what I was trying to say. possibly it has been removed due to being stuck in sport mode. The switch will bring the light on, assuming it works.

Hi Dieselman

The point that I am trying to get across is that there is no actual power feed or earth connection through the suspension switch to the warning state bulb.
This is so with all types of Hydractive ECU.
The switch is connected across two of the input lines of the ECU microprocessor.
The microprocessor has a dedicated output line that sends a low voltage signal to a switching transistor that provides the 12V feed to the suspension light.
The ECU low voltage lines are only fit for a maximum of 5 volt's and current in milliamps.
The typical voltmeter kicks out 9 volts on some test settings and will easily blow the protection on the ECU lines.
It is essential to unplug the ECU before poking around the wiring with a meter.

John

cromptons wrote: only issue I can see so far is the Braking sensor signal is always earthed, does this use sensor on the pedal or another one? .

Yes, sensor on brake pedal.

Also:

sensor on gas pedal
on steering wheel
on front antiroll bar
and 4+1 door switches are involved too.

Can you not read the faults through the 2-pin connector on the hydractive ecu with a led-type reader?

Well done for your purchase, that's a beautifull XM -I had also contemplated buying it!