Alarm Problem, Acitvated by ignition

[Assich]

Every so often when I turn the ignition off it turns the alarm on. The doors don't lock or anything like that, just the alarm switched on. I assume it is a rogue signal or bad connection somewhere. Any ideas?

[techmanagain]

What is the state of your battery? A low voltage often will trigger the alarm. If it's a big dicey, I suggest you change it before long. Mind you, a damn good clean up of the connectors on the battery and especially the earth connector on the engine (remove and clean, then Vaseline)
Works wonders very often.

[onthecut]

Hi all.

While we're on alarms, I've noticed with the new toy that on activating the central locking (and alarm, I presume), the indicators sometimes stay on, without flashing, for upwards of 20 seconds. No other indicator problems I'm aware of in normal use. Not had this on any of the previous Xms. Any thoughts ?

Mike.

[Assich]

Techmanagain - what from you've said I assume you've picked me up wrong. It is not the alarm going off that is the problem, it is the fact it is being set. Interestingly if I don't turn the ignition off all at once but only turn the engine off and leave switch in accessory position for a few seconds the alarm is not set when I turn the key to off and remove.

Onthecut - I understand that this is a "tell tale" to tell you the alarm has not been set because of a problem with it or more likely one of the sensors. Check to see if the red led on the dash to the left of the switches flashes. If it doesn't then alarm has not been set.

[Assich]

Been thinking - dangerous I know. Could it be the ignition switch itself. Have many people had problems with the switch?

[onthecut]

Hi Assich.

Cheers -- will check that out.

Mike.

[xmexclusive]

Hi All

Have been giving this a bit of thought!
I note Mikes warning that thinking is bad for your health.
Citroen made some changes to the immobiliser and alarm systems round about ORG 7000 that makes them operate slightly differently. The original Mk2 system was THACHAM 2 compliant and I think the changes took the system up to the next level of protection.

One of the changes is that "the device activates automatically with the ingnition off:
- as soon as the doors are locked or on opening the drivers door.
- Maximum of 10 minutes after switching off the ignition."

There seem to be 3 versions of the Owners handbook XM-GB-5006 all with alarm/immobiliser differences. One handbook has 2 different systems over successive pages but you are expected to sort out which one is yours. In the next years handbook they added a 30 second delay to the door opening.

Another difference was to change the garage code from 1111 to make it user selectable just like the main immobiliser code. A good number of cars fitted like this have been resold with just the garage code declared. They have the potential to become non starters if the battery goes flat or is disconnected and the system wants the (unknown) last main immobiliser code to restart.

On a more general note Techmanagain has raised the issue of poor battery voltage. I now suspect that voltage drop through poor connections has a much more profound effect on XM systems than we realised. Most modern electronics operates from 5 volts using a regulator so is virtually immune to battery variations. The XM stuff needs a good 12 volt supply and when this drops the circuit may well malfunction. Each poor joint in both the supply and the earth feeds may well add the resistance to drop half a volt or so. I suspect that a lot of XM kit when under load gets a lot less than its design voltage.

This effect would be most noticable in low voltage/low current circuits so lets consider the ABS sensors that work by generating a small signal. The circuit fails and a test shows the sensor at fault so this is changed for a new one. The act of changing the plug connection with new contacts one side will clean up the connection and may well remove the defective joint that was the original cause of the ABS problems. Does anyone test removed ABS sensors or do they just go in the bin.

Regards

XMexc

This post has been edited by xmexclusive on July 16, 2007 10:39 am

[Ciaran]

Hi folks,

Re the alarm arming itself when attempting to start.
My Xantia does this regularly, due to the fact its never used, and is only started occasionly to move it up and down the drive. Hence, the battery is weak. Quite a few times when turning the engine over, I get the alarm LED activating, basically the voltage dropping so low has caused the alarm ECU to go offline and reset. The default behaviour when power is lost then restored, is for the system to arm itself.
You can verify this happens, by removing one of your battery terminals, then putting it back on. Watch the indicators, because they will light up with the 'alarm arming' signal as soon as you touch that terminal back on the battery. This is by design.

I believe this feature is present to prevent the casual scumbag from just disconnecting the battery and getting around the system, of course it wouldn't pose much of a problem for a professional thief.

My S2 XM also did this for a few weeks last year when it had a dodgy battery in it. Had sporadic central locking problems too, which all went away by itself when I replaced the battery and wrecked terminal.
(Reminds me, must get round to changing the other terminal!)

As others have already said, the XM electrics rarely seem to get their alloted voltage, which goes a long way to explaining unpredictable behaviour if your battery is even slightly suspect. ABS faults etc, are probably caused by the same thing, maybe we should start testing the voltage going to some of these things, instead of just replacing them, as XMExc says!

Ciarán

This post has been edited by Ciaran on July 16, 2007 01:18 pm

[Assich]

I hear what you say and agree to a certain extent. I shall jsut emphasise that it is on turning off the engine and not when trying to start. More importantly from voltage drops it is when turning straight from engine running to off. As I said earlier turning to accessory from engine running and waiting a few seconds before turning to stop means the alarm doesn't wrongfully activate. Thing is what is the difference. I would have expected the voltage drop to be when turning engine off as no charge from alternator then. If that was the case then turning from running to accessory would set the alarm. The error codes came up with loss of signal from reciever but I assumed that was because the alarm had been disconnected. Perhaps not. The other thing that is taking me down a loss of signal or power route is the fact that if you disconnect the battery then on re-connecting the alarm is set. This happened on my previous XM but on that car the doors were also locked. The doors do not lock on the current car when re-conneting the battery. Earths are all good onj the car, I have checked them all and resistance is as good as nil. I think it is a bad connection but thought it may be the ignition switch having a bad connection.

[Ciaran]

Oh right.... that's certainly a puzzler then. I was just thinking faulty ignition switch maybe, but you've already started to suspect that one. I guess to rule it out you could try a spare switch if you have one, they're not hard to change.

Failing that, would the alarm continue this if you wired up a new supply to it? Might be slight overkill mind you...

Its really weird it only does it when turning off... I was going to go with XMExc's suggestion that they changed the alarm so it passively armed, as with many other cars of the era, however the fact it doesn't do it consistently negates that possibility...
Could it be that its supposed to do it consistently, but is faulty, and only engaging intermittently?

Ciarán

This post has been edited by Ciaran on July 16, 2007 03:51 pm