Focus mk3 2012 starts without a key, very strange problem!!

[adam_k12]

hi all, been having this very strange problem with a car i have recently purchased from auction. Has some minor damage on the offside wing, long story short it is very dirty inside at the moment has been sitting a while and it seems some water condensation may have crept in causing some mold on the interior. I dont want to touch anything as it is so im waiting to get a full interior deep clean done. I noticed the other day that the cars key fob is completely dead and doesnt lock or unlock the doors but for some reason always starts the car without a battery low message or having to hold it against the designated keyless area. I should note it is a keyless entry car. The other day i left the key at home and went to the car pushed the clutch down and it started as if the key is there?? ive never witnessed such a problem before the only thing i can think of is that theres another key fob somewhere in the car but i checked briefly and couldnt find anything. Has anyone ever seen anything like this or know what the issue could be ? also, once the car is started the instrument cluster displaying the revs and speedo works perfectly fine for the first five second and then the needles just drop. all the other lights are still working just the rev counter and speedo needles drop. Very strange problem any help would be appreciated.

[unofix]

The immobiliser system PATS is totally passive and does not use a battery of any kind.

There is a Transponder chip inside the keyfob which the car scans for and interrogates each time the keyfob is inside the car. Provided the transponder chip has been coded in to the car, then the ignition will start the car.

The keyfob battery is only for the remote lock/unlock and nothing else.

[unofix]

The 2012 Focus Handbook:

https://www.fordservicecontent.com/Ford_Content/catalog/owner_guides/ENUSA_CG3568_FOC_og_201201.pdf

[alexp999]

11 minutes ago, unofix said:

The immobiliser system PATS is totally passive and does not use a battery of any kind.

There is a Transponder chip inside the keyfob which the car scans for and interrogates each time the keyfob is inside the car. Provided the transponder chip has been coded in to the car, then the ignition will start the car.

The keyfob battery is only for the remote lock/unlock and nothing else.

If the battery in the fob is dead as OP says, then the transponder can only be read passively when it is in the "dead key" position. It works a bit like NFC, the power to wake the passive chip is very short range.

[unofix]

The transponder chip is passive. It has no means to connect to a battery as it is sealed inside of a little plastic capsule.

[alexp999]

5 minutes ago, unofix said:

The transponder chip is passive. It has no means to connect to a battery as it is sealed inside of a little plastic capsule.

Yes but my point was that OP said car is starting even without the key in the "dead key" spot.

If the key battery is dead, it will not be broadcasting its rolling code to start the car and the passive chip cannot be read from any distance, so it's not that which is allowing it to start either.

EDIT: With keyless and a working fob battery, the passive transponder is not being read. It is reading the code broadcast from the key instead. The passive chip only gets read when the key is in the "dead key" position. The car cannot detect the passive chip otherwise.

[adam_k12]

my problem is that even with the fob not being anywhere near the car, the car still starts. I left the key fob at home and came out to the car with NO keys and it still starts when i press clutch and hit the start button as if the key is with me when it is not, the car starts with NO keys present.

[unofix]

So taking on board the latest update from Alex,. As I see it there can only be 3 options possible:

(a) Your key while you left it in the house, was in fact still within range of the car. However, since you say there is no battery in it and the transponder would most definitely be out of range, we can rule this option out.

(b) There is as you suspect a second keyfob somewhere in the vehicle. It could have been dropped under a seat, be in the boot or gone down the side of the back seat.

(c) Someone has deliberately found a method to bypass the security so the car appears to start with out a key. A very simple way to achieve this would be to take a transponder chip that was coded in to the car. Then place it on the underside of the 'safe key area' that you place the fob when the battery is flat. This would fool the PATS system since it would always read the hidden transponder and allow the car to start.

Can anyone think of other ideas ? 🤔 

[alanfp]

My money is on (b) - ESPECIALLY if you only got one key with the car. 

Also....

6 hours ago, adam_k12 said:

I noticed the other day that the cars key fob is completely dead and doesnt lock or unlock the doors

So did it previously lock/unlock the doors?

Are you now locking/unlocking the doors with the metal blade?

[adam_k12]

2 minutes ago, alanfp said:

My money is on (b) - ESPECIALLY if you only got one key with the car. 

Also....

So did it previously lock/unlock the doors?

Are you now locking/unlocking the doors with the metal blade?

nope its never worked since i purchased it. the main reason i even attempted to leave the key at home and try to start it because it seemed like it was completely unresponsive to the key. ive had keyless entry cars before and usually when the central locking isnt working the battery is low or dead there will be a warning and it will ask you to place the key in the safe key area in order to start, that doesnt happen in this case. im getting the car interior fully cleaned tomorrow and hopefully they find another key inside but ive had a brief look and couldnt find it. starting to get worried because if there isnt a spare then this problem is extremely rare and i would have no idea what to do next.

[unofix]

Just had another thought which I can test in the morning on my car. If I leave a working keyfob inside my car, is it possible to lock the doors with my other keyfob. I'm guessing the car won't allow me to lock a working keyfob inside. 

[alexp999]

If another key is detected in the car it’s not supposed to allow it to lock. 

[DaveT70]

My money is on that there is another key inside the car or boot somewhere, that's why your passive (keyless) entry isn't working, because it doesn't work if the key is inside the vehicle.

How many keys do you have?

[unofix]

I can confirm that if a working keyfob is left inside the car then you can not lock the doors using the keyless handles or using the buttons on the keyfob.

So the conclusion would seem to be that the OP has a working keyfob somewhere inside the car. All he has to do now is find it 👍

[adam_k12]

ive just had the car detailed and can confirm there was in fact a spare key inside!! thanks everyone for the advice it was in the sun visor of all places !! never even thought to look in there but the key is also fully working with the central locking. as @unofix had mentioned the other key was not working due to the fact there was already a spare key inside the car. i now have 2 fully working keys so im very happy. thanks again to everyone for the help!!