Immobilised!

[keithbaker]

Hi, all

I had to call out the RAC yesterday. The car had been in the garage unused for a week. I tried to use the remote to unlock it, but nothing. Assuming the remote battery to be flat I unlocked the car with the key, and then attempted to silence the alarm by inserting the key into the ignition and turning it 3 times. This worked (although I think in less than 3 turns) but the engine would not then turn over. The immobiliser light by the cigarette lighter stayed on permanently, and very bright. I later discovered that when I press the romote fob the headlights (and no others) come on, and will stay on for as long as I hold down the button.The brilliant guy from the RAC spent an hour and a half with me, desperate not to be beaten (I think he liked the car!), but wasn't able to trace the fault. He did, however, manage to bypass the immobiliser and "hot-wire" the car for me. He's shown me how to do this, so if all else fails I'll be able to get it to a garage.

One thing to mention is that a few months ago I had a new (second-hand) light switch/indicator stalk fitted due to the failure of the original. As the headlight feature in this puzzle, could that be the cause?

Another train of thought - I discovered that the roof will not open, and given that the gearbox must be in park or neutral to start the car or to raise the roof, could this be the common denominator?

Any suggestions would be very welcome!

Thanks in advance.

[ChrisDixon]

Keith, first off I don't have any experience of facelift cars but similar experience with my X300 might be relevant. Assuming the Jag security systems are similar on cars of the same age:
1) the headlamps coming on when you press and hold the lock button on the remote is a standard feature, once the lights come on if you release the button they should stay on for 20 seconds or so; this also rules out a flat remote battery (but it wouldn't hurt to change this if it hasn't been replaced in the last couple of years).
2) try going back to the beginning i.e. lock the car with the key, then try unlocking it with the remote, if that doesn't work open it with the key then insert the key into the ignition within 10 seconds (the x300 alarm system bleeps until you do this) and turn the key to position II the dash lights should all illuminate but the starter won't engage if you turn it further, so turn the key back to position I, then to II again and see if it will then start. I've had to do this a few times in frosty weather lately,but my car had been parked outside. It may be the XJS system is completely different but worth a try!

With regard to the roof not opening this may be a red herring but there is an inhibitor switch in the starter circuit that prevents the car being started in gear, this could be an unrelated problem to the immobiliser, but then again it could be that when the immobiliser is active that part of the circuit is disabled!

Hope this is of some use, regards, Chris

[keithbaker]

Hi, Chris, and thanks for taking the time to answer.

1) I think I'm right in saying that it's the side-lights, rather than head-lights that flash twice when the alarm is dis-armed (perhaps someone could confirm this?)

2) I had the same thoughts as you about locking the car and starting again. I also disconnected the battery for a few minutes, hoping the system would re-set itself. Sadly to no avail.

My thoughts with the inhibitor are that both starting the engine and raising the roof are reliant on the gear lever being in either P or N, therefore if this has failed, might it not allow either?

Any other thoughts, guys?

[jthorne]

There is a bypass, turn on the car to the stage where the battery/abs lights etc come on. Do this 3x. This will deactivate the Jaguar immobiliser....

[keithbaker]

Hi, J

Thanks for this, but I did this initially, which turned off the alarm, but has not solved the problem. I've also disconnected the battery in the hope that it would reset, but to no avail. I'll have to get it to a garage when I have time.

[ptjs1]

Keith,

Sorry to hear about the problem. A couple of thoughts:

On your car there are three distinct security circuits:

- an alarm system controlled via the remote
- an engine immobiliser circuit controlled by the immobiliser "key" which fits into the slot below the ignition key (I assume you have this?)
- the engine (& hood) inhibition circuits, controlled by the rotary switch on the side of the gearbox)

From memory, the three circuits are not linked (I'll check the diags later)

It feels as if it's important that you work out what is causing the problem. It might be that you have two separate problems. The hood circuit doesn't care about the immobiliser, it needs to know that the transmission selector is in P or N, that the handbrake is on and that the key is in Pos II. Also from memory, the immobiliser circuit stops the engine from firing not from turning (at least that's what mine does. Again I'll check the diags later).

So if the engine won't turn and the hood won't operate, you might be looking for a fault in the rotary switch. Try wiggling the transmission selector through the positions in case it's getting slightly confused about where it is. I've seen this happen before. Alternatively, hotwire the wires on the switch (yes you'll have to get under the car) and see if you can get the car to start and the hood to operate.

Hope this helps. Give me a ring if you want to talk.

Good luck,

Paul

[keithbaker]

Hi, Paul

Thanks for this.

I'm going away for a few days tomorrow, but I'll try to work through your suggestions the following weekend, time permitting. BTW, I don't have the separate immobiliser key on this one.

I see you have an XJ8 Sovereign now. Funnily enough I've been lusting after one of those of late. I look forward to seeing it sometime.

Regards,

Keith.

[keithbaker]

And the answer is..............

Hi, All

Didn't get time to investigate the problem further myself, so took it into Clarke's in Heathfield for them to sort out. It turns out that a short had blown the alarm security system module, meaning a replacement was necessary, as well as another remote control. Not cheap, but it's great to have the car working properly again!

Thanks to all for their suggestions.

Regards,

Keith.