PROBLEM GONE AWAY!: Central Locking and Immobiliser not working after changing battery

[PJAB]

Hi

I have recently had to change the battery in my car. All seems good - except that now the key fob doesn’t seem to control either the immobiliser or the central locking.

I only noticed this just before I set off for work today - so haven’t had time to investigate at all.

Any clues on where I should start? I can operate the central locking using the key in the door lock - so I am thinking that it must be more to do with the receiver circuit for the signal from the key fob - because it is the key fob signal that seems to be ineffective.

The immobiliser is a Foxguard system. I will check whether the other fob works - but I don’t think that is likely to be the issue because the red LED in the key fob illuminates and I think that means that it is correctly transmitting.

Any thoughts / hints / tips appreciated - I am due to go on my first big trip in the car this Friday and I only have a bit of time to sort this on Wednesday. I could do the trip without sorting it - but it would be really nice to have it sorted by then.

Thanks in advance

Peter

[poprivet]

Usually with Foxguard there is an isolation key switch in the glovebox.

If all else fails, switch this off and operate the central locking with the normal door key in the drivers side.
I have a wiring diagram for the unit which I can send to you if you need it, I would rather not put it on the website for security reasons.

[PJAB]

Usually with Foxguard there is an isolation key switch in the glovebox.

If all else fails, switch this off and operate the central locking with the normal door key in the drivers side.
I have a wiring diagram for the unit which I can send to you if you need it, I would rather not put it on the website for security reasons.

Thanks very much - I am away from home until tomorrow night but I will have a prowl around when I get back and let you know when I find. I really appreciate your advice and offer of help!

Peter

[JimMann]

Are you sure the key fob battery is up to scratch? That would seem an obvious first / simple change to investigate. Simply because the red LED illuminates does not necessarily mean the fob is transmitting correctly.

Jim Mann

[PJAB]

Are you sure the key fob battery is up to scratch? That would seem an obvious first / simple change to investigate. Simply because the red LED illuminates does not necessarily mean the fob is transmitting correctly.

Jim Mann

Hi Jim

Good question - I will be checking that by seeing what happens when I use the spare key fob - both of which worked a week ago.

Thanks

Peter

[poprivet]

It will be like this when opened,

12v battery.

[PJAB]

Hi All

I’m pleased to report that this issue is now resolved - or rather it is currently (no pun intended).

Thanks to a call from a fellow forum member, I removed the trim covering where I expected to find the Foxguard controller. As it happens, I couldn’t see any such controller - but the wiring in there included a couple of what I would describe as “dodgy” connections.

I had a look at them - but decided to leave it all until after my trip to Norfolk this weekend in case I made matters worse in a “rush” to solve this problem. I have already learnt that any sense of rushing a job on the XJ-S is likely to lead to a sub-optimal outcome - or even damage - so I am trying to develop some self-discipline about pulling back if I feel my “get it sorted now” instinct kicking in!

I was parking the car back in the garage after cleaning her - when the alarm went off! Oh good I thought - at least there’s some sort of circuit. I cancelled the alarm with the key fob. I checked the other key fob - both controlled the immobiliser and the central locking as they should - so I was seemingly in the clear.

However, I know that I am not PROPERLY in the clear because I do not know why the circuit is now working properly. There is the possibility that fiddling with the wires behind the trim MAY have just happened to make a circuit good or break a bad circuit - but that seems a bit far-fetched to me - I’m not a big believer in fairies at the bottom of the garden etc.

Time will tell how long the key fobs continue to operate the relevant circuit. Hopefully by the time the same problem reoccurs my knowledge of the car in general will have advanced a bit more and I’ll be able to investigate in a more logical and informed manner - using sensible techniques.

In the meantime - thanks to my lucky stars and all those who chipped in to this forum. I’ll let you all know if the circuit fails again!

All the best

Peter

[PaulGover]

As computer geeks like me know, one way to placate the fairies is to unplug and re-plug every connector. That wipes the oxide off the contacts and restores dodgy connections (having disconnecter power, i.e. battery first).. For extra points, spray with contact cleaner. And, of course, take action if any of the connectors appear iffy.

[PJAB]

As computer geeks like me know, one way to placate the fairies is to unplug and re-plug every connector. That wipes the oxide off the contacts and restores dodgy connections (having disconnecter power, i.e. battery first).. For extra points, spray with contact cleaner. And, of course, take action if any of the connectors appear iffy.

Indeed - but I haven’t actually worked out where the wires are or indeed the controller as yet because, somehow, I didn’t need to. I suspect that challenge will present itself at some stage though …. !

Thanks

Peter

[Andy P]

Hi Peter,
Fingers crossed the issue doesn't come back too quickly,if at all.
Well done for getting stuck in.
Enjoy your car,
Take care.
Andy

[PJAB]

Hi Peter,
Fingers crossed the issue doesn't come back too quickly,if at all.
Well done for getting stuck in.
Enjoy your car,
Take care.
Andy

Andy

Indeed - I hope so - my mind is now turning to looking at the next issue!

Peter