Hi all

I bought a 2007 2.5T Mondeo Estate Titanium X last week and a couple of days after there was a message on the dash saying "Alarm System Service Reqd". I've searched and found other people saying there is a battery backup sensor or backup alarm under the FNS wheelarch which gets wet and causes this error. The message only showed the once - has not been seen since. The weather has been lovely of course and I'm yet to wash it so there's been no water near the car.

I have a 3 month warranty with the garage where I purchased the car, however this warranty is with them only, so I have to drive 70 miles each way leaving wife and kids without car (school run etc) plus the time off work, so it's a pain to say the least. I plugged in my ELM327 to the OBD2 port to see if there were any fault codes, but none were reported.

What I'd like to know is your opinions the following:
Would a proper Ford diagnostics device pick up on the alarm error when my ELM327 would not? If someone knows for sure that the dealer's equipment will find no errors if I can't find any then that makes my trip less worthwhile.
If the message shows once, is it likely to return and eventually cause (expensive) problems?
Any further advice on this error message?

The difficult thing is, the warranty expires just before Christmas, so I've not got long to sort out any problems that arise. I suspect diagnosing and replacing these alarm components could be a bit pricey, so don't want to leave it, however if it weren't for the warranty I'd currently be simply keeping an eye on the messages to see whether it comes up again rather than taking it in to be checked over.

Thanks in advance.

Worth adding that without the message displaying anymore I'm expecting a wasted journey, PLUS it's £10 per day for the 'courtesy' car. My preferred local garage will lend me an old KA or old Rover for free. Proper job! Not sure I'd want to do 140 miles in them mind.

For the benefit of anyone searching for this same issue I took the car to the dealer who sold it to me after the message reappeared a few times and they did some extensive testing and found that the backup alarm module (or something like that) had totally failed. It is back in for the new part this week and I will ask them to see whether they can protect it from water (by moving it / covering it (if safe) / re-routing the water if applicable etc) as this appears to be the reason for these failures.

So to answer my own questions. Yes it was worth the trip (they spent probably at least a couple of hours on diagnosis and I dread to think how much the part costs), their diagnostic capabilities obviously far outweigh those of my cheapo ELM327 lead and software and they were able to diagnose even though the message was intermittent and not displaying when they had the car.

£60 petrol for the two trips but much cheaper than waiting for the alarm to fail and paying for it myself.

Hope that helps someone with the same problem.