Can you start the car with only the metal key?

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SeaCrosser
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Post by SeaCrosser » Wed May 04, 2022 6:54 pm

That's the short version.

The longer one is that I was upside down at the time, reaching into some rock armouring at the local harbour to remove plastic rubbish.
The key fob slipped out of my pocket, clipped my ear then split into two when it hit the shingle. I was able to retrieve the metal bit of the key, but the black plastic part of the remote was further into a shallow cave.

Back at my car I opened the door, then the boot, to get a litter picker grabber out. The alarm went off and wouldn't stop.
I realised that I actually don't know how to start the car with just the key. Or can it be be done?

I obviously retrieved the remote, reunited it with the key and all was well.
Can anyone help?
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Juan Sheet
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Post by Juan Sheet » Wed May 04, 2022 7:08 pm

The engine ECU will be locked and needs to handshake with the transponder chip in the key fob before it will authorise the engine starting. So although you can access the vehicle with the key, you won't be able to start it.

As a result, the alarm is triggered when you open the door with the key.

So that's why the alarm goes off, but you can't start the vehicle with the key alone.
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SeaCrosser
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Post by SeaCrosser » Thu May 05, 2022 6:49 am

Thanks @Juan Sheet

So I guess that means the pull-out, proper key is only to get you into the car, in the absence of a working battery.

I read somewhere, you hold up the transponder near the steering column, for it to be recognised. Are you saying that would that work ( and the car would start) even without the battery?

I've had a fair few "Key not detected" warnings in the last six months.
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Beanee687
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Post by Beanee687 » Thu May 05, 2022 7:42 am

You need the fob as that has the immobiliser chip in it. In some fobs that is a small black cube near the key blade in others it's on the PCB in later fobs. If you find the cube you have to tape it to the steering column shroud so it deactivates the immobiliser. If you have a keyless entry/start car then you have to hold the fob PCB against the column on the flat portion on the left hand side to start car.
You really need to get the fob back.
If in UK then Timpson's can make spare fob for you providing you take V5C and ID. You have the metal key for pattern.
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Juan Sheet
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Post by Juan Sheet » Thu May 05, 2022 12:56 pm

SeaCrosser wrote:
Thu May 05, 2022 6:49 am
Thanks @Juan Sheet

So I guess that means the pull-out, proper key is only to get you into the car, in the absence of a working battery.

I read somewhere, you hold up the transponder near the steering column, for it to be recognised. Are you saying that would that work ( and the car would start) even without the battery?

I've had a fair few "Key not detected" warnings in the last six months.
Yes correct. The key is for emergency access to the vehicle for example in case of a battery or electrical failure or the fob got dropped and damaged for example - it means that you can get into the car. They key can also be used to lock and unlock the vehicle. Even in the last scenario where the fob may have been dropped, the chip inside the fob will continue to work if held by the keyless recognition pad on the left of the steering column for keyless entry systems - but of course cannot be used to start the car without the transponder chip present.

To answer your other question, the chip inside the fobs are coded to the vehicle and the same chip cannot be re-coded. On a keyless entry system the fob itself sends a wireless signal out that the vehicle's various aerials dotted through the car pick up to allow the doors to be unlocked and the alarm deactivated. If the remote fob battery fails, you would gain access with the emergency key, which would likely set the alarm off. The you would hold the fob against the keyless reader on the left side of the steering wheel column and this would energise the chip in the fob and allow starting / switch off the alarm.
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SeaCrosser
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Post by SeaCrosser » Thu May 05, 2022 3:09 pm

Beanee687 wrote:
Thu May 05, 2022 7:42 am
You need the fob as that has the immobiliser chip in it. In some fobs that is a small black cube near the key blade in others it's on the PCB in later fobs. If you find the cube you have to tape it to the steering column shroud so it deactivates the immobiliser. If you have a keyless entry/start car then you have to hold the fob PCB against the column on the flat portion on the left hand side to start car.
You really need to get the fob back.
If in UK then Timpson's can make spare fob for you providing you take V5C and ID. You have the metal key for pattern.
Thanks Beanee

I hung upside-down into the hole, reached into the hollow underneath with the grabber and hooked the fob back within reach. (Before the tide came in!) I do this 4-5 times a week all along the coast. I really need a foolproof way of securing my key, so I don't be so careless again. :roll:
Very useful info about the procedure though.

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SeaCrosser
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Post by SeaCrosser » Thu May 05, 2022 3:13 pm

Juan Sheet wrote:
Thu May 05, 2022 12:56 pm
SeaCrosser wrote:
Thu May 05, 2022 6:49 am
Thanks @Juan Sheet

So I guess that means the pull-out, proper key is only to get you into the car, in the absence of a working battery.

I read somewhere, you hold up the transponder near the steering column, for it to be recognised. Are you saying that would that work ( and the car would start) even without the battery?

I've had a fair few "Key not detected" warnings in the last six months.
Yes correct. The key is for emergency access to the vehicle for example in case of a battery or electrical failure or the fob got dropped and damaged for example - it means that you can get into the car. They key can also be used to lock and unlock the vehicle. Even in the last scenario where the fob may have been dropped, the chip inside the fob will continue to work if held by the keyless recognition pad on the left of the steering column for keyless entry systems - but of course cannot be used to start the car without the transponder chip present.

To answer your other question, the chip inside the fobs are coded to the vehicle and the same chip cannot be re-coded. On a keyless entry system the fob itself sends a wireless signal out that the vehicle's various aerials dotted through the car pick up to allow the doors to be unlocked and the alarm deactivated. If the remote fob battery fails, you would gain access with the emergency key, which would likely set the alarm off. The you would hold the fob against the keyless reader on the left side of the steering wheel column and this would energise the chip in the fob and allow starting / switch off the alarm.
I had a good look and didn't read this in the manual. I'm grateful for the explanation and I suspect it will benefit more than just me.
Cheers!
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Beanee687
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Post by Beanee687 » Thu May 05, 2022 3:47 pm

Put a tie wrap through the fob key ring. Then fasten the tie wrap so it forms a loop. Undo your waist belt and pass the end of the belt thru the loop and do your belt up again.
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Juan Sheet
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Post by Juan Sheet » Thu May 05, 2022 4:09 pm

Here's my solution!

Basically it's a leather key fob designed specifically for the C3 Aircross fobs. Once the fob is put inside the leather cover, you affix the metallic bar through the leather and through the fob ring and out the other side. Then the key metal arch you see attaches to the threaded bar and is secured by a screw to lock it down.

The buckle part has a spring clasp that you push in, so that you can attach it to a belt loop on your trousers or elsewhere. I attach mine to the belt loop and then pop the fob inside my trouser pocket. I don't worry about it while I'm out as it's always attached to me. Everyone who has seen it (including those at Citroen this morning) think it's a great idea.

Not only does that. but the leather sheath also protects the fob itself from scratches, knocks and affords some protection from drops.

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If you are interested, about £7 including delivery from the Far East :D

https://www.aliexpress.com/item/4001114 ... 8021%7Csea
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Tommo
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Post by Tommo » Thu May 05, 2022 7:14 pm

Juan sheet, does this leather key fob case protect against being scanned?, i personally use this one i purchased off Amazon, i have tried to open the car with it in the pouch and it does actually work,, it won't open the car. And obviously it's left in the pouch overnight as it protects against the car being scanned.

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