Car Key Or Battery Problem? bizarre mystery!

[Waldo 96]

This is totally bizarre...

 

My car (a Peugeot 107) has 2 keys; a main key with buttons for remote lock and unlock, and a spare key with no buttons, which just works as an old-style car key, put it in the door and turn to lock or unlock.

 

The other day, the button on my main key for 'unlock' fell out (lucky I noticed and found it on my driveway); so I buy a replacement case for it on eBay, thinking I can just transplant the inner PCB with battery, and metal bar part of the key that goes in the ignition.

 

So, this replacement case arrives this morning, I put the it together with the PCB and metal bar part of key, and test it locking and unlocking remotely; all worked fine.

 

This evening, I get in the car to go somewhere, and using the main key (with new case from eBay etc), it just doesn't start, I try like 5 times. No joy. Never had a problem with the car not starting in all the time I've had it. I go get the spare key, and try that, starts up fine, first time.

 

When I arrive at my destination, I turn engine off, and try starting it up using main key, nope, try again with spare key, works ok.

 

Had a discussion with a chap at the event I was attending, and he seemed to think the battery could be low, anyhow, I get back to car, hoping it's going to start (and not leave me stranded) and it starts up first time using my spare key.

 

Get home, try multiple times, switching between main (transplanted) key and spare key; each time, main key fails, and spare key starts up first time.

I then reassembled the original main key (removing the case I got from eBay and replacing with original case), tried that 3 times, and it worked every time.

 

How can this be?

 

Surely it's just the bit of metal that's going in the ignition, and the PCB isn't doing anything other than locking and unlocking the doors remotely? So how can just changing the case making it not work?

Edited February 9, 2022 by Waldo

[Dardandec 32]

Have a check in the old case and make sure you haven't left the transponder chip in it, that activates the immobiliser. it could be in a little slot in the old case. 

[Janus 28]

Either that above,

OR could it be that on the occasions that the original key failed, you maybe had the 'button  battery in the wrong way round.

[Waldo 96]

1 minute ago, Janus said:

Either that above,

OR could it be that on the occasions that the original key failed, you maybe had the 'button  battery in the wrong way round.

Thanks all.

 

The battery stays connected to the PCB as you remove it from the case. I suspect other poster maybe on to something though, I didn't notice anything else inside the original case, but now I think about it, the eBay advert mentioned something along those lines.

 

Transponder must be pretty small?

 

Thanks again!

[Mr Bloke 1,445]

10 minutes ago, Dardandec said:

Have a check in the old case and make sure you haven't left the transponder chip in it, that activates the immobiliser. it could be in a little slot in the old case. 

Hmmm...

 

Yep - I would say that's likely to be the problem.

 

You could test it by holding the old case near the new one when you try to start the car...

 

... if it starts you know the transponder is 'hidden' inside the old case!

[Waldo 96]

Does the transponder need to be right next to the ignition?

[Mr Bloke 1,445]

Just now, Waldo said:

Does the transponder need to be right next to the ignition?

Yep - pretty close I would think.

[Dardandec 32]

The key reader is usually a ring fastened to the key side of the ignition barrel. As Mr Bloke says get it as close as possible to that area. Hold it at the side of the new one when starting.

[Arthur Ritus 30]

Transponders don't use the battery, they get power from the coil that reads them (like how a toothbrush charges)

I would guess yours is a separate transducer - they are sometimes built into the RKE chip, when the case came apart and the battery fell out the transponder did also, have a look around where you found the battery for a small black liquorice torpedo or coffin looking thing. Have a look at pictures of them on google. If you can't find it you will have to have a new one programmed for your car, transducer and programming only should be around £20, I wouldn't leave it too late, the spare goes faulty / lost and you will have to call someone out which will be a lot more expensive.

[Waldo 96]

45 minutes ago, Arthur Ritus said:

Transponders don't use the battery, they get power from the coil that reads them (like how a toothbrush charges)

I would guess yours is a separate transducer - they are sometimes built into the RKE chip, when the case came apart and the battery fell out the transponder did also, have a look around where you found the battery for a small black liquorice torpedo or coffin looking thing. Have a look at pictures of them on google. If you can't find it you will have to have a new one programmed for your car, transducer and programming only should be around £20, I wouldn't leave it too late, the spare goes faulty / lost and you will have to call someone out which will be a lot more expensive.

Thanks Arthur,

 

The transponder is still in the original case, its separate from the PCB and battery. I can take it out of the original case, and pop it in the new case, but fearful it may be a bit fragile, don’t want to break it prying it out.

[alchresearch 215]

The ID46 chip - just prise it out, its a robust little thing.