S2 Xantia Activa - immobiliser probs

[wheeler]

... when we're talking about 'the transponder' do we mean the chip in the key?

And ... if that's the case then where 'should' it live?, Andrew: you asked me to check that' it's still there, but where's 'there'?? I can;'t see anything other than a key blade and solid shoulder to the key, is it inside the plip itself?

The transponder is the chip in the key, on the flip out type key it lives in the head of the key blade & its moulded inside the plastic bit, I would think on this type of key it would be pretty impossible to get it out.

Wheeler: when i interrogate the CPH state it shows a '1' against all items except the injection ecu which shows as '0', i interpreted this as being unable to talk to injection ecu due to having no handshake with the key, are you saying that even with a duff key it should still be readable? I did also try and read faults from t the engine ecu (are the two names, engine and injection ecu, the same item?) aside from the CPH dialogue but this also came back as unable to contact the ecu?

Yes the injection ECU & engine ECU are the same thing but the injection ECU is a more accurate description. When i asked about the dialogue with the injection ECU i mean by going directly into it, not through the CPH. If you have a duff key or pickup aerial etc you should still be able to talk to the ECU & read fault codes & live data etc. When the ECU is 'locked' it just means the engine is not authorised to start.
If you cant even get any comunication with the injection ECU the chances are its missing a live feed or earth.

[superloopy]

... when we're talking about 'the transponder' do we mean the chip in the key?

And ... if that's the case then where 'should' it live?, Andrew: you asked me to check that' it's still there, but where's 'there'?? I can;'t see anything other than a key blade and solid shoulder to the key, is it inside the plip itself?

The transponder is the chip in the key, on the flip out type key it lives in the head of the key blade & its moulded inside the plastic bit, I would think on this type of key it would be pretty impossible to get it out.

Wheeler: when i interrogate the CPH state it shows a '1' against all items except the injection ecu which shows as '0', i interpreted this as being unable to talk to injection ecu due to having no handshake with the key, are you saying that even with a duff key it should still be readable? I did also try and read faults from t the engine ecu (are the two names, engine and injection ecu, the same item?) aside from the CPH dialogue but this also came back as unable to contact the ecu?

Yes the injection ECU & engine ECU are the same thing but the injection ECU is a more accurate description. When i asked about the dialogue with the injection ECU i mean by going directly into it, not through the CPH. If you have a duff key or pickup aerial etc you should still be able to talk to the ECU & read fault codes & live data etc. When the ECU is 'locked' it just means the engine is not authorised to start.
If you cant even get any comunication with the injection ECU the chances are its missing a live feed or earth.

Understood, thanks

So, in this case I seem to have a myriad of problems because i'm assuming that a faulty injection ecu (problem 1) would have no bearing on whether my key can be read or not (problem 2) ?

Cant for the life of me see how the two problems could be afflicted at the same time as all that has literally happened has been a battery refresh which has been done many times without any problems

The car 'lives' up the drive and hasn't had any road action for some time, she has been started and aerobicised on many occasions though without any hint of a problem and now we have a hatful, strange eh?

Maybe the elcectrical diagrams will provide a good starting point, mind you i'll need talking through these as well, including how to use a multimeter

Is it worth mentioning that the airbag ecu is also incommunicado, should i be able to access this via lexia, maybe points to a common problem, common inasmuch as shared with the injection ecu? I've checked all fuses (under dash, under bonnet, are there any more hidden?) and they all read as 'good'.

[wheeler]

So, in this case I seem to have a myriad of problems because i'm assuming that a faulty injection ecu (problem 1) would have no bearing on whether my key can be read or not (problem 2) ?

Cant for the life of me see how the two problems could be afflicted at the same time as all that has literally happened has been a battery refresh which has been done many times without any problems

I would say there is only one problem, the injection ECU is not powered up. This will in turn mean the CPH cant verify the code in the injection ECU matched the one in the CPH.
I'll give a breif & simplified overview of how the imobiliser works which might help you understand whats going on. This applies to a petrol xantia 2 but the diesel is similar.
The componants in the system are the injection ECU, the CPH, the transponder reciever aerial (the little ring round the ignition barrel) and a transponder chip moulded inside the key.
The ECU, CPH & transponder chip are all coded with a matching code (T4FE in this case). The ECU has a wire connection to the CPH & the CPH has a wire connection the the transponder aerial. The transponder chip has a wireless connection to the aerial when its close enough.
With the ignition off the ECU is in the locked state which means the fuel injectors wont be operated by the ECU if you were for example to force the ignition barrel with a screwdriver.
When you get in the car & switch the ignition on a few things happen all very quickly, the ECU & CPH are both powered up, the CPH sends a request code to the transponder chip via the aerial, the aerial powers up the chip & asks it for its code, the chip relplys with T4FE, the CPH recieves the code & checks that it's the same as the one it has, great the CPH also has T4FE, The CPH sends a coded signal to the ECU to request its code, the ECU replys T4FE the CPH replys thats my code aswell & the ECU unlocks & is authorised to start.
It then goes without saying that if the ECU cant talk to the CPH then it wont authorise starting.
I think straight away we can rule out a faulty or uncoded transponder chip, a faulty aerial or the wiring between the CPH & the aerial. If any of these were at fault the key light on the dash would flash rapidly with the ignition switched on. Reason is the correct code is not recognised.
You can simulate this fault by either disconnecting the aerial or shielding the head of the key with tin foil.
If the light is not coming on at all this sugests the ECU is not talking to the CPH.
Possible reasons for the ECU not talking to the CPH:-
A faulty ECU.
ECU not being powered up due to missing live feed or earth.
A faulty CPH.
CPH not being powered up due to missing live feed or earth.
A broken or shorted wire connection between the ECU & CPH.
Initially i would rule out a problem with the CPH or it's power supplies due to the fact that Lexia can talk to it & some of its other functions still work.
The fact that you can't comunicate with the injection ECU with Lexia would make me look at this first. If the wire link between the CPH & ECU had a problem it would not stop lexia comunicating with either of them.
My money here is on either a live feed or earth missing from the injection ECU.
EDIT: just thought of 2 possible causes of missing supplies to the injection ECU that are quick & easy to check. A faulty double injection relay (big brown relay next to the ECU), I see you have other xantias, only takes a few minutes to swap them. Other check is to make sure the inertia switch has not tripped.

[superloopy]

Thanks wheeler, I'm beginning to get my head in gear. Now then .. this brown relay, where should it be? Is it around the box where the injection ecu lives because I can't find it. I have another active, would the part be interchangeable if I can locate it. Can't see anything that looks like a relay under the bonnet?

[addo]

On some cars, the relay is black. It's in the same box as your ECU normally.

[wheeler]

Should look like this, as addo says it may be black also, they should interchange no problem as long as they are both the same colour.
I believe is in the same box where the ECU lives on a xantia.

[andmcit]

There's a large sliding red clip that pulls sideways off the multiplug unclipping
the relay from the loom and IIRC on the Activa the relay is brown - I've been
messing with a V6 Xant lately which has two - the lug shown in wheeler's pic
slides into a slot moulded in the ECU box.

BTW - LEAVE THE AIRBAG ALONE!! There's around 50 small bolts holding
the airbag onto the dash frame and you'll have spent more time undoing
them than getting at the CPH - anyhow why do you need to remove the CPH?
It really does sound like there's no power feed to the Injection ECU as
suggested by Wheeler - this matches the feelings with my V6 and the other
V6 mentioned (Green Goblin).

[superloopy]

Thanks guys, there's a black box headed 'bitron' on a bracket in the ecu box, this it? All I've got in there are a couple of ecus, small white filter looking thing and this black gizmo seated on its own bracket. Yup, I'll leave the passenger airbag alone, cheers!

[wheeler]

Thanks guys, there's a black box headed 'bitron' on a bracket in the ecu box, this it?

That sounds like it, it should have 15 pins on it. does it look the same as the pic apart from the colour ?

[superloopy]

Ok, have swapped over the relays, both black btw, and nada, zilch, key icon still not illuminating.

Another quick question, at switch on, you need all three items ie both ecus and transponder chip, to be present and correct to even get the light to flash, however briefly? If any one was missing would the light not flash constantly or am I wrong? It's looking more like as you say, earth or power problem. I'll need to wait a nd see what Jim can post up. Is there any prep work I can be getting on with in the meantime, I know nowt about electrics but always willing to learn ....

[CitroJim]

Mike,

I'll try hard to get the diagrams up latert today although I'm a bit pushed for time..

[superloopy]

Jim, lurking in the wings eh!

There's no urgency at all, the heavens have opened here and its an ark I'll need soon, not an activa!!

Any suggestions on prep work and just where I begin gratefully accepted.

[CitroJim]

Jim, lurking in the wings eh!

Always lurking Mike Not always in a position to post though

Right, here are all the diagrams you may need.

As per usual, you have the schematic, the harnesses and the locations.

Firstly, Injection:

RGX Injection Circuit

RGX Injection Harnesses

RGX Injection Locations

Immobiliser (CPH):

Immobiliser Circuit

Immobiliser Harnesses

Immobiliser Locations

The CPH unit in the above is Item No. 8630, 0004 is the immobiliser light and 8220 is the aerial unit around the key barrel.

Finally, the Central Locking. This is controlled by the CPH but a separate part of it.

Central Locking Circuit

Central Locking Harnesses

Central Locking Locations

They're a bit complex to read but basically the circuit is a theoretical schematic diagram, the harness diagram shows how the units and modules are interconnected and the Locations diagram shows the location of the units and their earth points and so on.

I'd begin by checking all fuses involved are good and have power on both ends of them. From the diagrams you can deduce which are live all the time and which are ignition switched. The ignition switch is shown in the off position.

Earths are show as codes. The CPH Earth is shown as MC51 in the circuit. If you look at the location diagram you'll see the earth is physically located under the centre console.

On the harness diagrams look for rectangular boxes in the harnesses with a designation such as E822A. This is a splice (joint) in the loom and these can corrode and give trouble and it is quite possible a splice has given up. E822A is, for instance, a splice in the wiring between the Injection ECU and the CPH.

The location diagrams shows the location of splices and E822A can be found in the loom between the ECU box and the IC02 interconnect plug on the inner wing (Injection Location Diagram Diagram E)

Study the diagrams Mike and all will start to be clear. They look scary at first but are really very logical and well done. The haynes BoL has a useful table of all the module/unit ID numbers for cross reference purposes.

Armed with those and after you've done the basic voltage checks, come back to us and let us know what you see.

[wheeler]

Do you have a test lamp with a proper filament bulb (not an LED type) ?
This would be best to use along with a voltmeter. A voltmeter can show 12v but not enough current to light a bulb.
You want to be checking for a permanant battery live feed at pin 18 of the ECU & an ignition feed at pin 37.
You want to check pins 19 & 24 for a good earth. Remove clean & refit earth point MM03 which looks like its on the front of the gearbox from the pic but not very clear.

[CitroJim]

I'm not sure off-hand where MM03 is exactly but I can check on mine.

Also a good idea to check all the earths on the multi-earth plate on the LH inner wing - the one where the battery earth terminates. This plate can get a bit corroded...