Simon's new Xantia V6 and Leaf blog

[Mandrake]

Thanks Steve. Eight pages to explain the immobiliser ? sheesh !

[Hell Razor5543]

Think yourself lucky it is only eight!

[CitroJim]

Simon, the V6 is certainly happy to have the keypad disconnected. Do it whilst the engine is running and it'll not be needed again. Do make a note of the last code as if you ever want to reconnect it you'll need it.

To reconnect a pad without knowing the code is fatal.

Make a note of it in marker pen on the ECU...

[Mandrake]

Thanks Jim, but is the code stored in the immobiliser or the engine ECU ? If you were to swap immobilisers between two cars (not that I plan to) would the code stay with the same car or would it go with the immobiliser unit ? Just trying to understand how it functions...

[CitroJim]

The code is stored in the ECU Simon. I've proved this is the case on both diesel and petrol versions The keypad does not remember codes in any meaningful way.

The immobiliser functions are all built into the ECU on an S1, unlike the S2. The keypad communicates with the ECU over a serial communications link.

The only ECU that cannot have a keypad disconnect is the TCT/Activa one. Don't know why...

[Mandrake]

So when you enter the code the keypad unit just sends the code to the engine ECU which unlocks, and then some period of time after you turn off the key the keypad unit sends a "re lock" command to the ECU ?

So by unplugging it while running it never gets a chance to send the "re lock" command so the ECU stays unlocked...cunning

[Northern_Mike]

Thanks Jim, but is the code stored in the immobiliser or the engine ECU ? .

I know for a fact it's in the ECU as I've swapped keypads between cars in the past. Disabling it is easy, and quite honestly, getting round it is hardly the work of a genius, especially on a TD!

[Northern_Mike]

So when you enter the code the keypad unit just sends the code to the engine ECU which unlocks, and then some period of time after you turn off the key the keypad unit sends a "re lock" command to the ECU ?

So by unplugging it while running it never gets a chance to send the "re lock" command so the ECU stays unlocked...cunning

Got it in one Simon.

[Mandrake]

I might unplug mine then, although leave it physically in place for now since I don't have an oddments tray to fit. I really find remembering to enter the code a pain, especially when you can't see the buttons past the gear lever without leaning right over...(brilliant design there, the gear lever obscures both the keypad in park AND the sport mode LED in drive... )

It might be in good nick and be low mileage, but nobody is going to steal a 17 year old Xantia!

[CitroJim]

It might be in good nick and be low mileage, but nobody is going to steal a 17 year old Xantia!

Don't be so sure. I had a dream last night that someone stole my Activa and replaced it with one in terrible condition; full of rust, water leaks and odd wheels...

[xantos]

Correct me if I am wrong, but I read somewhere that unplugging the keypad works as long as you don't disconnect the battery...

[Trainman]

As promised......

[KP]

Jim, you think the TCT ecu could be unlocked in the same way some pugs are unlocked by just disconnecting the ecu while the engine is running? Then disconnect the keypad turn it all off, plug the ecu back in and unlocked ecu is done? I'm sure this is the process used on 306 gti's...

[KP]

You'd be surprised what the parts of one could be worth abroad, lost cars are stolen for parts these days as they are much easier to move on.

[CitroJim]

Correct me if I am wrong, but I read somewhere that unplugging the keypad works as long as you don't disconnect the battery...

You're right Xantos and it works on all but a TCT Activa for reasons nobody knows.

Will, one of the ECU specialists can unlock one at a cost...