Hi all

Dont worry there are plenty more daft questions to come

I unplugged the immobiliser keypad on the mk2 turbo i got while it was running so i wouldn't have to re enter it, but does this mean if the battery gets disconnected i have to plug it back in to re enter the code, or do i never need to reconnect it now?

Next question, my mk1 has a plug for an immobiliser keypad so i guess it was one of the extras available for my model?, out of pure curiosity i am dying to plug it in, and yes, i do have better things to be doing but................ .
Anyway if i plug it in will i just have to enter the 0001 initialisation code that it says about in the owners manual or will it do nothing or lock the ecu?.
I have a couple of spare ecu's so im not bothered if it does but if no one has tried it i may give it a go, what do you think?

D

Hi Dean,

Your first question, no, disconnecting the battery doesn't reset it.

Derek

Hi Dean

The code is stored in the ECU as well as the keypad status (installed/not installed) so when you start trying a replacement ECU everything depends on what was done with codes and installation status with the previous car. So if you did not recover the ECU yourself and a secret code was enabled but not written on the ECU then the chances of finding it by trial and error are 1 in 9998. With a 30 minute lockout after three wrong tries it could take a persistant few weeks of boring effort to get back in. Thats why the specialists can get away with charging £50 upwards to read your ECU for you. If you still want to play test the replacement ECU's first and if you cannot make them work in your cars think long and hard before you start moving or modifying your two good ECU's from their respective paired engines. It used to be that every now and again XM's would turn up on ebay as lost the immobiliser code cannot now start it. I guess these days they go straight to scrap.

John

Hi John

I know the code for the turbo's ecu but my prestige (n/a) has never had a keypad fitted, the ecu's are staying with the engine's just wanted to put the keypad from the turbo mk2 into my car, which was never fitted with one from new, while it still has its original 20i engine in ..........well, i want to see if it works more than anything cos im sad .
So as you have said the code is stored in the ecu does that mean an ecu that has never had a keypad fitted will just require following the initialising sequence in the handbook,? I know my ecu will immobilise the car with the alarm, but will the keypad conflict with the existing alarm system or work with it?


Thanks for the help so far.

D

Well i plugged it in, i couldn't resist and it does........................ nothing but sit there with the red light flashing slowly car starts as normal but the keypad seems to think the car is locked up with the engine off all the time.

D

Hi Dean

I do not know. It all depends on the progression of software and hardware development by Citroen during the XM production run. For the 2.5TD ECU's that I have done some checks on there were at least four different programme versions in the first two years of production some with the same part number so you cannot be sure what is going to happen (or not happen) if you swap ECU's. For this age of electronic design the owner variable features like the keycode will be stored in non volitile memory on the ECU (stays good with no power) but can be rewritten/changed on the car. The ECU controlling programme is stored in an EPROM (fixed memory chip) and cannot be reprogrammed in the ECU. It might be that all the ECU's had keypad capability from day one and it just sits there benign if the car does not have the feature. Alternatively and more likely there might have been ammended ECU programmes when a new feature was added. Chances are that a later ECU will run in earlier car but an earlier ECU might not run a later car.

Edit Note: Took me a while to actually complete and send the above post by which time you had tried the keypad. If you want to try the later ECU you can get away with unplugging the one on the car but leave it in the box. Then plug into the temporary replacement and lay if across the top of the cars ECU's. I have even managed to drive around like this while testing functionality.

John

Thanks John

D