Electronics 2000

Its my car and perfectly legal to hot wire it.

The ignition its self presents no problems, take the barrel out with a slide hammer ( a slide hammer is used for dent pulling, car body work).

However...

The key has a chip thingi, which must be there to enable the ECU.

I think the ECU sends a signal to something in the steering column then switches it off, the key chip oscillates in resonance, when the signal is switched off the chip continues to oscillate and sends a signal back to the ECU. I think... I am not sure but...etc.

Which wires does it use and how can it be bypassed?
How can I find the signal and replicate it?

Tar&stuff.

If you look inside a car key there is a small glass tube, it is not part of the circuit board which opens the doors, if the battery is off and circuit board removed, the only thing in the key is the glass tube...it still starts the car.

It seems to be a tuned circuit, it looks like a coil on some magnetic core and I would guess a capacitor, this would only oscillate when it receives a signal at frequency of resonance.

The transmitter ( guess) switches on and of frequently, may be if it does not receive a reply signal it does not switch back on until the ignition is switched off and back on.

As far as I can see, a scope attached to a small antenna close to the tube might give the frequency, but then if it only switches once for a fraction of a second I would need some sort of digi device with a memory.

What digi device?

Or set up a signal generator circuit and just go through a range of frequencies switching the ignition on every once in a while, if it is fine tuned, and I suspect it is, this will be very time consuming.

Any better ideas?

Where is the transmitter?

Tar&stuff.

Might of cracked it.

Set up a signal generator, and switch it on and off at highish frequency and monitor the tube with a scope.

May be... Hmmmmm.

Any better ideas?

Tar&stuff.

If I can do that then I have the signal frequency and can trace it back to the ECU.

The manufacturers are likely to have hidden the transmitter, and perhaps a receiver. I suspect the airbag but... ...?
I don't see any unaccounted for wires except the 3 to the airbag, I have not tried disconnecting them...yet.

I have a Chinese oscilloscope which plugs into a laptop, it did not work on my old laptop, I have bought an old/new one ( due to the coffee incident) I will see if I can get it to work, along with a SIG gen ( not yet acquired).

Any better ideas.

Tar&stuff.

When I press the button on the key, maybe it is amplified so maybe I can pick it up from that.

Tar&stuff.

Right well I'm just gonna stop talking to my self on this thread until I get some equipment set up.

May be there are two resonant circuit's in the tube ( 2coils +2caps ), because then it would be FM, I think that makes more sense or my key would open several doors in any carpark if the door opening circuit uses the tube.

I will get a hand full of keys from the scrapyard one of these days and find out what I can, I don't want to distroy my own only key.

I don't like the manufacturer effectively having my car keys and having to rely on them if I lose my keys, I was quoted over £300 for a new key when I lost my only one last time, fortunately I found the key.

Well that's about it, any sugestions welcome.

Tar&stuff.

One final thought, it is perhaps not a good idea to mention specific makes and manufacturers for legal reasons on this thread, photos are to be avoided. I am not a lawyer but my car belongs to me so it is perfectly legal to do with it as I please.

Back to this thread when I know more.

Tar&stuff.

The aerial which talks to the immobiliser chip in the key is usually a round thing around the outside of the ignition barrel. I thought the keys were individually coded, i.e. the key is inserted into the ignition and turned to ign. The ECU sends some AC electricity to the aerial thus charging the capacitor in the key. The key then sends back it's code and if the code matches that in the ECU it allows the car to start.
I believe you can get keys duplicated in Timpsons for some car where they clone the code in the key to a new one.

I have dissected another key, it has a similar tube ...the tube is oil filled and has a coil a small circuit board with two resistors and a coil, there is a bit of hard black stuff on the back ... don't know what is under the black gunk.
There is no power to the tube, I think the ignition causes it to oscillate and then picks up the oscillations, its like a coil on a core, the direction of the core is (I think ) a factor.
I will get back to this when I have more time.

Tar&stuff.

I think it is powered by the aerial which, on my mondeo is around the ignition barrel. Probably a bit of AC magnetism which is picked up by the black tube in the key thus powering it and allowing it to send a signal back to the aerial.
A bit like those anti theft things on the doors in shops. I know they go off if you try and take a coil of wire through them such as a telephone extension lead