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Mondeo Various Faults - Immobiliser Active & Alarm Service


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Hi All,

A long story but upon buying the car 2 years ago we straight away had "immobiliser active" warning on the dash but the car still started (warning usually came up after car turned over), the garage we purchased it from had it back and said it was a low voltage on battery and they replaced the battery for a new one, the fault then went away for a few months.

A few months later "immobiliser active" then came up, but again let's the car start fine and usually comes up just after the car has started. The warning comes up once a week and there doesn't appear to be any pattern (eg not always after a short trip), we've taken to just ignoring it and it being a minor nuisance as it doesn't stop the car from working. Effectively been ignoring it for 1 3/4 years.

A few weeks ago we started the car and got the "alarm system service required" warning, but I have read is either an internal ultrasonic sensor or water in the battery backup in the passenger wheel arch (or failed battery in backup). Again this doesn't stop the car from working, however I guess the alarm is no longer working. I did lock the car and sit inside, move around a lot and the alarm didn't go off.

I'm just wondering if the two error messages are linked to each other? I got both error messages at once this morning (but again car started and drove fine).

I was going to attempt to take a look inside the battery backup box to see if there is any corrosion on battery or water ingress, but am just thinking whether I am going to make things worse and the car may actually immobilise?!?

I attempted to talk to my local ford dealer, but they were very rude and unhelpful and couldn't even offer any advise and atoned £80 just to look at the car!

Any advice offered would be great, mondeo is a 10 plate, so a bit over 5 years old and is 60,000 miles. Always been serviced by us and previous owner (company car).



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I had this issue after I was tinkering with my car and elmconfig. If you just bought the car, I am wondering if someone before you did something similar.

I would start by disconnecting the battery for 60 minutes and reconnecting, this should drain all the components and start it again, hopefully that should resolve it, but if it does not, I would suggest you get elm config, and a modified elm327 lead, go get your AS BUILT data and reload the gem with it.

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Is the battery a silver calcium type? As if it's a standard lead acid this could be your problem since it will be fine initially with a lead acid but the alternator will fry it due to the output charge and this causes all sorts of faults to occur

Sent from my iPad using Tapatalk

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Thanks for the replies.

I'll take a look at the car tonight and see what the battery type is, as the garage wasn't a ford garage (car supermarket type place), I doubt it would have been a silver calcium and probably just whatever standard battery they had in!

The car was previously a company car, although this doesn't mean it hasn't been tinkered with I guess! I'll take a look at the lead and software you have recommended and see if i can an figure out what to do!

Cheers so far.


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