I find that if I lock with the button on the key and then apply the deadlock immediately after - as the book instructs - the alarm sounds after 30 secs and the key unit has to be used to unlock to stop it. The red warning light on the dash also flashes at a a rate of knots. I then relock without the deadlock, and the red light does not flash at all on the dash.. Is there a quick cure?

Hi techman,

Your description of the symptoms makes it sound as if there's a fault in one of the door switches or the internal ultrasonic detectors.

The late XM's were multiplexed, some as early as 1997. If yours is one of them then you'd be able to get it plugged into the computer. If you're lucky there might be a fault code stored in the ecu or if the fault is present at the time then you'll find out what it is. Its certainly worth a try. When I've had mine plugged into DJ's Elit, I remember seeing the intruder alarm on one of the menus.

Is there anyone near you with an Elit or Lexia?

cheers

noz

They call him "Noz the Knowledgeable". Where would we be without him?
The Elit test will be done shortly - I too have friends! Many thanks for the tip, Noz

I forgot to mention that I took my VIN number into the local Main Dealer and he looked it up on his (spare parts) computer. He established that it was non-multiplex.( And non-ABS ,which I knew).
One anomaly showed up; the Citroen record said my RP was 7759 when the A pillar stencil plainly said 7760!

Hi Techmanagain

Pleased to see you have found a replacement XM and that you are staying loyal to the 2.5 estate.
I guess that if lunch of french bread, brie and wine was good that day then during the afternoon you might just forget to use that days stencil on the odd car or three. Quality control might just have noticed next morning by which time the stencil had changed.
It seems sensible as Noz suggests to see if there is a record of a faulty component in the system.
There are at least two types of alarm/immobiliser system fitted to Mk2's. The change was in 1996. That year two different versions of the drivers handbook were issued with the variation in the alarm instructions. XM-GB-5006 and XM-GB-5006/2. In my experience not all UK cars got the correct handbook supplied. The later alarm has different/longer delays, push button reset, a 2 code memory system, and the ability for the Plip to over-ride the keypad. The alarm isolating key switch on the front scuttle is not fitted to cars with the later system. On occasions the later alarm seems to object to the car being locked with the Plip and unlocked with the key in the lock. A number of these later cars are sold on set to a garage code without anyone realising that there is a second unknown and overriding owners code. All is well until the battery is disconected or the new owner tries to change the code. On of the joys of buying an XM without full service history.
Multiplexing started in XM's with a batch of the original 1994 Mk2's supplied to loyal French customers. In the following year some UK XM's have the odd function multiplexed. In the following years progressively more functions were multiplexed on an individual model basis.
As far as I am aware the multiplexing was only used to avoid increasing the number of wires in a loom. This allowed new functions without needing to change the existing loom design.
Multiplexing and the fault socket are NOT related functions.
Early XM's had few working pins and many blank pin holes hence the limited number of functions measurable. Over time with new production Citroen increased the number of pins wired and the functions measurable on the different models.
If pin H3 of the fault socket is wired then the ECU can be read for immobiliser/alarm faults.

Regards

XMexc

Hi all,

XMexc is right to point out my faux pas. The multiplexing does not need to be related to the ability to interrogate an ecu. The multiplug from the Elit can talk to those individual ecu's which are wired out to the multiplug without needing to be multiplexed. The software inside the Elit must be able to choose the right pins on the plug depending on what ecu you choose from the menu. Clever stuff !!

I'm not sure the addiditon of multiplexed nodes wouldn't need a change of loom though. If a component was normally powered and controlled and then changed for the multiplexed variant the wiring would change very significantly. The BUS is 4 wire (presumably 2 of them being power) and then the new controller must "control" the outside world with the use of more wires. I'm totally guessing at this because I've never studied the multiplexing system in depth.

As for your errant RP number, some french wine is quite strong and if taken on an empty stomach on a Friday......

Sorry to go a bit off-topic techman but how did you get on? Even without the multiplexing you should still have been (or will be) able to connect to the alarm ecu.

Cheers

noz

alarms and locks? ive had my 2.5 three years now and always used the plip to lock it and dead lock/set the alarm. cos the locks are seized up, god knows what will happen if the remote packs in, i also spent a day trying to find out why the fuel flap would not lock, even changing the solonoid ?still would not work, ???? then one day when i was realy getting p%&&*£d off with it my daughter said /its the filler cap/ its getting in the way of that little thing that shoots out of the hole, yeah right i said, go and make me a cuppa pet,, gues what it was the fuel cap,, if you over tighten it it obstructs the pin that locks the flap, there must be a quote or something to cover that, but im! saying nowt,

Hi Splez

Changing the door locks is a 2 minute job. I can retumbler a set to suit any supplied key. If you do nothing else then change the drivers door lock for a working one with a key that you keep away from the car for emergency purposes. Breaking into an XM is difficult without doing some damage.

Regards

XMexc