Wiring Diagram Citroen Xsara Forte

[Joemoonlit]

Ok thanks for letting me know. So looking at the wiring diagram i can see there is a wire from the battery, passing via MF1 to pin 2 on the double relay(1304), and then pin 10 on the double relay goes to pin 52 on the ECU. Could this be the route of the 12V supply?
I could test the 12V supply to the relay and see if it has any voltage. I know there is no voltage at pin 52 as i tested all 55pins with the voltmeter.

However, like you said if the relay is faulty the car wouldn't start!

So possibly we could be looking at a faulty ECU maybe? Again i would presume if the ECU was faulty the car would not start. Is that right?

We are left maybe with the temp sensor.

If you have any further ideas please do let me know. My first task is to check the temp sensor, and i also want to check the continuity from pin 7 on the OBD2 port to pin 31 on the ECU connector, as previously i had tested this and continuity was positive at pin 30. Is there any way that this wiring diagram could be the wrong one? Although you identified the RP number and my understanding is that this should ensure the correct wiring diagram is used.

Thanks again for your input. You have been such a help. It does feel like sometimes i am never gonna get to the bottom of this issue. Fingers crossed i can get there.

[wheeler]

Again i would presume if the ECU was faulty the car would not start. Is that right?

Not necessarily, components inside the ECU can fail that may allow the engine to run but maybe not correctly.

This should be the correct diagram based on your RP number however its not unknow to find a few mistakes or typos.
Always confirm the wire numbers shown on the diagram by each wire when doing checks

[Joemoonlit]

Hi
Quick update:
- I c checked the continuity from pin 7 K line on the OBD2 port and pin 30 gives a positive signal. Pin 31 is actually a blank on the ECU connector.
So not sure what is happening there and compatibility with the wiring diagram.
- I tested the temp sensor and bingo. It's not functional.
I measured resistance when cold which was around 1750 ohms. A bit low I thought as specs say around 2000-3000 is usual. It is a hot day so possibly that could impact. Then I started the engine and monitored the resistance. After about 7 minutes the resistance increased to 2750 ohms.
Then it pretty much stayed there. I tested for 25 mins so engine was nice and hot. I understand that when hot the resistance should be between 300-500 ohms. So by the looks of it the temp sensor is dead. Would you agree?

In terms of impact on the car I understand that it could cause the fan to come on permanently and mess up the CO, HC and lamb emission readings. So I will replace the temp sensor and see what happens.

For the OBD2 port I did read that The Sagem SL96 ECU sometimes doesn't support generic OBD2 even if it has the connector and that it may only respond to Lexia/DiagBox (PSA) tools. Do you have any ideas on this?

[wheeler]

- I c checked the continuity from pin 7 K line on the OBD2 port and pin 30 gives a positive signal. Pin 31 is actually a blank on the ECU connector.
So not sure what is happening there and compatibility with the wiring diagram.

That's interesting as according to the diagram pin 31 connects to pin 2 of the crank sensor.
Can you confirm the wire number you have on pin 30? should be 133.

Without teaching you to suck eggs are you definitely looking an the pin assignments properly on the ECU plug? Is each pin marked or is it just the end one on each row then you need to count along?

[Joemoonlit]

I added a photo of the connector. There don't appear to be any marks to indicate which pins are which. However, looking at the picture i have assumed based on avrious sources that pin 1 is top left on the first row at the top of the picture. There are 18 connections on this row. Then Pin 19 is on the far left on the second row. If you count along you will see that Pin 31 is empty.

[wheeler]

There will definitely be a marker to identify pin1 at least, they are normally tiny but it will be there, there is normally one at the start & end of each row.
If you flip that connector 180 so the bottom right pin is now top left if you count it that was pin 31 is populated.
Again checking wire numbers will confirm.

[wheeler]

If this diagram from Haynes is correct then you have it upside down & bottom left (I think) on your picture is pin 1

[Joemoonlit]

Thanks for this. I will take a closer look at the connector to see if i can see any markings. Temp sensor comes Monday or Tuesday next week, so will give an update once i have fitted. All being well i can get an emission test and it will make a difference.

[Joemoonlit]

I made an incorrect assumption about the temp sensor I was testing and it turns out that there are 2 sensors on my car:
A green temp sensor and a brown. The brown sensor is likely used by the fan control logic, which interprets its PTC signal to control fan speeds or cut-in thresholds, not by the ECU directly. The green sensor connects to the ECU.

I cannot see the brown sensor on the wiring diagram you provided early on in this thread, however I think I can see the green sensor that connects to the ECO: 1220 on the wiring diagram.
Would you know if there is a separate wiring diagram showing the brown sensor? It supposedly either connects to the Bitron relay near the fan or directly to the BSI. In my model it says likely to the Bitron relay, however, I don't know. If I had a wiring diagram then I could check where this sensor connects to.
If you know of the wiring diagram and can share it would be very much appreciated.

[wheeler]

The Brown temp sensor is for the cooling fans & A/C (if fitted) and yes its PTC type. It will connect to the 'bitron' unit which if i remember right is under one of the headlamps on a Xsara.
The Green sensor for the injection system is NTC type.

[Joemoonlit]

I have seen a black plastic box under the nearside wheel arch towards the headlight. I guess that could be a good contender. The wiring looked ok, as in no signs of corrosion, but I will look at how I can test and see how it goes.

In the interim I have ordered a lexia 3 diagbox 7.83 diagnostic connector to see if I can connect via the OBD2 diagnostic connector. Supposedly it should connect to my 2000 year model. Maybe that will give me some more insight.

I just need to solve this issue with the fan being on constantly that may be the reason for failed emission tests.

I also noticed the radiator is leaking down the side so may need a new radiator as well now. Not gonna change right now though as not bad enough to stop it running and unless I can get to the bottom of why the car fails the emission test it cannot get through MOT. So trying to limit money spent until I solve this.

Thanks again for your help.

The diagnostic tester doesn't come for a couple of weeks so will likely post an update after that. Unless I can sort the fan in the interim.

I almost forgot, any idea where the AC control unit might be. I may need to test this considering it's linked to controlling the fan along with the brown sensor.

[Paul-R]

If you're installing the Diagbox software from scratch you have to go through a series of version updates. If you're only using the equipment on a 2000 vehicle then there's no need to go beyond very 7.57. This will be sufficient for vehicles even up to about 2014 or so. I used this version on my 2015 Peugeot 308 with mostly success.

[wheeler]

I cannot see the brown sensor on the wiring diagram you provided early on in this thread, however I think I can see the green sensor that connects to the ECO: 1220 on the wiring diagram.

The reason you can see the brown temp sensor it is because its part of a different system, it just for cooling fan control. The green sensor is for the injection system & can have a direct effect on fuelling & engine idle speed etc. I can't see the brown sensor affecting emissions. On later multiplexed models there is only a single sensor that does it all. I forgot about the older systems having the separate sensors. Some also have a separate blue sensor just for the temp gauge on the dash.

[Joemoonlit]

Paul-R : It's good to know it worked on an older car. thanks for that information. I believe the one I ordered comes with 7.83 software which I have read is the most stable version and best used on older cars like mine. Hopefully it works, but if not then I will see if I can roll back to the version you mention.

Wheeler: Yes I realised it was likely not on that wiring diagram as it was part of another system. Not sure if you have the wiring diagram of the system that the brown sensor is part of? If one was available I wanted to get access to it so I could see if it went to the Bitron relay or directly to the BSI. Although you clarified it goes to the Bitron relay so I will first work on that assumption.

Yes I think mine has a separate blue sensor but I would need to take another look to confirm.

Thanks both for your input

[wheeler]

Here is the cooling fans diagram. 8010 is the 'Bitron' unit. There are actually 2 diagrams listed & look yery slightly different, i will let you check that more in depth about what the differences are. At a quick glance it looks like it may just be the fuses it uses.
The BSI is very basic on these early Xsaras & only really has anything to do with some internal comfort functions.
As you can see it doesn't even appear on the diagrams for fuel injection or the cooling fans.