MK1 172 immobiliser wiring/question

[Dan@SJM]

Now, ive got the wiring loom in my hand, and from the decoder ring ive got 3 wires, ones an earth and the other 2 go to 2 different plugs on the UCH, now, does this mean the immobiliser is in the UCH? or it goes through the UCH into the ECU? so i could potentially run the ecu with out the decoder ring etc etc?

The way i had seen it before this is that the immobiliser is set into the ecu, the ecu sends a code when turning on the ignition, and reads the code from the key.

But now seeing this, its either as above or, ignition is switched on, then the UCH checks the code on the key, and depending on the code being matched, sends the OK signal to allow the ecu to fire up and run the engine?

ANy help much appreciated.

 

[16v_jon]

The ECU and UCH are linked together the imobiliser program runs in the ECU but the UCH has checksums for it.
the way you explained it above is exactly right- but you need to run the decoder ring.

are you putting the engine in a valver?

 

[Dan@SJM]

Do i have to run the UCH? if not, how do i get around it with the decoder ring running into the uch, do i just find the PIN data on the ecu, and cut out the uch completely?

 

[Dan@SJM]

Has anyone got the ecu pin data to hand?

 

[BrianR]

You cant just pin it out, its written into the software, whats the problem, don't you have the key with the matching txpndr ?

 

[RSTuning]

I can disable the immo if you are interested

Paul

 

[Dan@SJM]

You cant just pin it out, its written into the software, whats the problem, don't you have the key with the matching txpndr ?

I do have the key etc, but the loom is going in a different car, which doesnt have the decoder ring fitted as standard.

 

[BrianR]

You cant just pin it out, its written into the software, whats the problem, don't you have the key with the matching txpndr ?

I do have the key etc, but the loom is going in a different car, which doesnt have the decoder ring fitted as standard.

Then take the chip out of the key, glue it to the decoder coil and stick it up behind the dash... or if you can get the coil round the new lock, swap the transponder chip over into the new key.

 

[Dan@SJM]

I understand that, but its going in a valver, so im trying to get rid off all the loom i dont need, like the uch.

 

[BrianR]

I understand that, but its going in a valver, so im trying to get rid off all the loom i dont need, like the uch.

Right, Im lost then, I dont know my way round a 16V.

Which is the part thats causing you the problem, is it the UCH to ECU connection you are trying to get rid of, so you can dump the UCH.

 

[Dan@SJM]

Ah i see, well the 16v ecu immobiliser is deactivated by the plip of the key, the 172 one as you say is read by the decoder ring, i want to know what wires from the ecu read the decoder ring so i can get rid of the uch, I havent looked into the wiring side on the valver yet but it doesnt seem to bad, its a case of keeping the majority of the valver wiring, and just connecting the ecu to ign live and leaving the valver wiring to work the fuel pump etc.

So all i want the 172 wiring to do is run the engine, not control anything else.

 

[BrianR]

Got it, let me see what I can find out for you..

 

[BrianR]

Right, this is the 16v layout, does this help ?

 

[Dan@SJM]

That will help when it comes to doing the wiring on the valver, have you found anything on the pin data on the 172, ive got part numbers of the ecu if you need it

Dan

 

[RSTuning]

Pin 83 is the coded line to the UCH as i remember. Regarding the PM if this method was used it should be fine with no UCH.

 

[BrianR]

Here you go Dan....

 

[BrianR]

Pin 83 is the coded line to the UCH as i remember. Regarding the PM if this method was used it should be fine with no UCH.

Did you mean pin B3 ?

 

[Dan@SJM]

Ideal, im forwarding those diagrams onto my electrician mate who will hopefully figure it out!!

 

[RSTuning]

Pin 83 is the coded line to the UCH as i remember. Regarding the PM if this method was used it should be fine with no UCH.

Did you mean pin B3 ?

On the ecu and plug the numbers continue rather than A1, B1 etc. I will double check tomorrow

Paul

 

[BrianR]

I think you will find its B3 Paul, there are only 22 pins on the de-coder unit and they are split into A & B to correspond with the top and bottom rows of the plugs (very silly way of doing it imho)

 

[RSTuning]

Nope i deffo mean what i said, the ecu is numbered 1 to 80 odd. But as you say on the system it's A/B

 

[BrianR]

Which control unit module do you mean then Paul ?

 

[RSTuning]

I mean the actual ECU. I have the details at work but i'm sure it was 83. I'll PM you a pic to show you what i mean

Paul

 

[Dan@SJM]

Heres my living room currently lol:

Ive decided to keep the 172 dash, and just cut out all the wiper/light wiring etc that isint needed so all im running on the 172 loom is the engine, dash and immob.

 

[Dan@SJM]

Does anyone have the Engine computer PIN data?

 

[Dan@SJM]

bring up this old thread again, does anyone have the pin data to the block connector of the bulkhead?

 

[Dan@SJM]

right, just been cutting most of the loom out and i think ive finally nailed this immobiliser decoder, Ive traced 3 wires, 1 negative, 1 redwire then goes to a 5amp fuse in the fuse box then one goes into the UCH, now, if i cut it at each end of the uch, would it work still or does it need the UCH to decode it?