Citroen XM - lost contact with ECU

[white exec]

OK, some helpful info there.

Reading back over your posts, you list three things not right:
- unable to get Lexia to communicate with suspension (Valeo) ECU
- unable to get Lexis to communicate with engine (injection) ECU
- suspension ECU not powering up when IGN is switched on
and keypad showing fault (Red+Green)

There could be a fault with Lexia (or its interface or connections to the car), but assuming there isn't, as it seems to check other items ok.

First check out the suspension ECU
This is a bit more straightforward than the Inj ECU.
Look at Gabor's Suspension circuit diagram (580-1/21e in my copy).
Unplug the susp ECU, and check that
- black connector, pins 1 & 2 are both getting permanent +12v live from F34 (mainboard)
- black connector, pin 5 is getting +12v from F7 (mainboard), when IGN is switched on
- white connector, pins 15 & 8 are both connected to good Ground (check with multimeter)
- and if you can, that white connector pin 5 is connected to Diagnostic Socket, pin 30
All those connections can be seen on Gabor's page.

Then, look at the Bitron double relay:
It needs to be supplying power to the Injection ECU.
You have checked that power is arriving at the supply side of the Bitron relay, with pins 2,8,11,14,15 going live. This is all correct.
What you need to do is check what is coming out of the Bitron double relay, as this supplies the Inj ECU.
- Unplug the Inj ECU, but leave the Bitron relay in place
Look at Gabor's circuit for Engine, 2.1TD

With IGN OFF:
- Find pin 7 on the black 15-way Bitron relay connector, and briefly touch it to Gnd. You should hear the relay click. Check that the same happens when you Gnd pin 45 on the disconnected black 55-way Inj ECU connector.
- When the relay clicks in, it should produce +12v on pin 5 of the Bitron connector (and pin 48 on the disconnected ECU connector)
- Do the same test (listening for the same click) on pin 4 of the Bitron relay connector. Check the same happens on pin 47 of the Inj ECU connector.

Now to the second relay in the Bitron double...
With IGN ON:
- Briefly Gnd pin 10 on the Bitron connector, and you should hear this second relay click on. Check that pin 40 on the disconnected Inj ECU connector does the same thing.
- Check that it brings +12 to pin 9 on the Bitron connector, and to pin 20 on the Inj ECU connector.

Note: For the 55-way Inj ECU connector, you will need to properly find the pin numbers marked on the connector. Will be numbered 1-55.

The anti-theft keypad [#176] is supplied with +12 (from the IGN sw) to its pin 13.
It also needs to see a +12 supply to its pin 14, coming from the Bitron relay pin 3.
Check that it is getting these two +12 feeds. Again, see Gabor's diagram for this.
_________________

The checks above will show whether the Bitron double relay is working properly, and feeding supplies to
the Inj ECU connector, and the Keypad.
There's a lot to check, but worth doing carefully and writing down the results.

Let us know what you find.

Connections from the Inj ECU to the Diagnostic Socket [#280] are also shown on Gabor's diagram:
ECU pin ---> Diagnostic pin
44 ---> C3
30 ---> C2
4 ----> C1
25 ---> B3
You could check these for continuity. Probably not at fault, as trouble here would not cause the engine not to start.

[Mateusz]

Reading back over your posts, you list three things not right:
- unable to get Lexia to communicate with suspension (Valeo) ECU
- unable to get Lexis to communicate with engine (injection) ECU
- suspension ECU not powering up when IGN is switched on
and keypad showing fault (Red+Green)

Exactly, + engine wont start
completing the story: During this time i fixed Lucas epic fuel pump. I took it out and put it in (now its third time in this year), but wiring from pomp (if broken) couldnt cause no power on suspension computer

There could be a fault with Lexia (or its interface or connections to the car), but assuming there isn't, as it seems to check other items ok.

Lexia works fine, i using this stuff regular and never had problems with connection to ecu and suspension.

Look at Gabor's Suspension circuit diagram (580-1/21e in my copy).

You mean circuit_diagram.pdf from here? http://citroen.tramontana.co.hu/en/the- ... am-project

Unplug the susp ECU, and check that
- black connector, pins 1 & 2 are both getting permanent +12v live from F34 (mainboard)
- black connector, pin 5 is getting +12v from F7 (mainboard), when IGN is switched on

ummm... Valeo computer i checked (in my previous post) and there was no tension anywhere

What you need to do is check what is coming out of the Bitron double relay, as this supplies the Inj ECU.
- Unplug the Inj ECU, but leave the Bitron relay in place

in previous post i also check Lucas Epic computer when Bitron relay was in place.
result:
Third test i plug in only #3 bitron and tested:
#1 Lucas epic computer - Powered pins: 11 , 18 (midle line counted from left, picture bellow)

Note: For the 55-way Inj ECU connector, you will need to properly find the pin numbers marked on the connector. Will be numbered 1-55.

I couldnt find stamped numbers on the ECU connector, have you somewhere pic how its correctly marked?

[white exec]

That's the correct document - Circuit Diagram pdf.
Good idea to print it out.

If the suspension ECU is getting no power, that needs investigating first, as it should be easy to do.
Likely that you only have ONE fault in the system, and that is to do with power supply, as it it affecting so many items. So worth looking at where power is coming from for the susp ECU, and sorting that.

Then do the checks I listed on the OUTPUT from the Bitron relay, because this supplies both the Injection ECU and pump.

[Mateusz]

it took a while but is done
Green colour - Good
Red colour - Bad

First check out the suspension ECU
This is a bit more straightforward than the Inj ECU.
Look at Gabor's Suspension circuit diagram (580-1/21e in my copy).
Unplug the susp ECU, and check that
- black connector, pins 1 & 2 are both getting permanent +12v live from Fuse F34 (mainboard)
- black connector, pin 5 is getting +12v from Fuse F7 (mainboard), when IGN is switched on
- white connector, pins 15 & 8 are both connected to good Ground (check with multimeter)
- and if you can, that white connector pin 5 is connected to Diagnostic Socket, pin 30 (i dont know which pin is 30, Diag socket has marks A,B,C ..... from 1-3)
All those connections can be seen on Gabor's page.

Then, look at the Bitron double relay:
It needs to be supplying power to the Injection ECU.
You have checked that power is arriving at the supply side of the Bitron relay, with pins 2,8,11,14,15 going live. This is all correct.
What you need to do is check what is coming out of the Bitron double relay, as this supplies the Inj ECU.
- Unplug the Inj ECU, but leave the Bitron relay in place
Look at Gabor's circuit for Engine, 2.1TD

With IGN OFF:
- Find pin 7 on the black 15-way Bitron relay connector, and briefly touch it to Gnd. You should hear the relay click. Check that the same happens when you Gnd pin 45 on the disconnected black 55-way Inj ECU connector.
- When the relay clicks in, it should produce +12v on pin 5 of the Bitron connector (and pin 48 on the disconnected ECU connector)
- Do the same test (listening for the same click) on pin 4 of the Bitron relay connector. Check the same happens on pin 47 of the Inj ECU connector.

Now to the second relay in the Bitron double...
With IGN ON:
- Briefly Gnd pin 10 on the Bitron connector, and you should hear this second relay click on. Check that pin 40 on the disconnected Inj ECU connector does the same thing.
- Check that it brings +12 to pin 9 on the Bitron connector, and to pin 20 on the Inj ECU connector.

Note: For the 55-way Inj ECU connector, you will need to properly find the pin numbers marked on the connector. Will be numbered 1-55.

The anti-theft keypad [#176] is supplied with +12 (from the IGN sw) to its pin 13.
It also needs to see a +12 supply to its pin 14, coming from the Bitron relay pin 3.
Check that it is getting these two +12 feeds. Again, see Gabor's diagram for this.
Incognition OFF - (1)live
Incognition ON - (1,13)live
_________________

The checks above will show whether the Bitron double relay is working properly, and feeding supplies to
the Inj ECU connector, and the Keypad.
There's a lot to check, but worth doing carefully and writing down the results.

Let us know what you find.

Connections from the Inj ECU to the Diagnostic Socket [#280] are also shown on Gabor's diagram:
ECU pin ---> Diagnostic pin
44 ---> C3
30 ---> C2
4 ----> C1
25 ---> B3
You could check these for continuity. Probably not at fault, as trouble here would not cause the engine not to start.[/size]

[white exec]

" Now to the second relay in the Bitron double...
With IGN ON:
- Briefly Gnd pin 10 on the Bitron connector, and you should hear this second relay click on. Check that pin 40 on the disconnected Inj ECU connector does the same thing.
- Check that it brings +12 to pin 9 on the Bitron connector, and to pin 20 on the Inj ECU connector. "

This is an important fault:
- Are you saying that second relay isn't clicking when you ground pin 10?
Pin 40 (ECU) should connect direct to pin 10 (Bitron) - see diagram - so both pins should do the same thing...make the second relay click.
- Is there +12 on pin 2 of the Bitron relay when the IGN is switched on?

Check this ↑ first.
Will return to Suspension ECU later/

[Mateusz]

- Are you saying that second relay isn't clicking when you ground pin 10?

I check this on 40 ECU pin and bitron dont click. I dont tested this directly on 10 bitron pin because it needed unplug then i loosing power and couldnt check. Actually i have bitron out of the car. Want check him direct from car battery. 2 live & 10 ground to make him click?

- Is there +12 on pin 2 of the Bitron relay when the IGN is switched on?

Yes, pin 2 live. For sure i can check him again tomorrow.

Edit
Make it directly from battery 2+ with 10- and its click

[white exec]

Edit
Make it directly from battery 2+ with 10- and its click

Right, looks as if we're getting to the bottom of it.

Pin 2 getting its supply from IGN switch - good.
When pin 10 is grounded, relay clicks - good.
When pin 40 (on ECU connector) is grounded, relay doesn't click.

That last means that the wiring connection between 10 and 40 is broken. Check it with a meter on the car, with ECU and Bitron unplugged. If there is no continuity (or some other resistance), then you will need to run a new small cable from 10 to 40.

Cable failure is rare (unless it has been modified or interfered with), so check very carefully the connector pins (male and female) at each end before giving up on the original cable.

[Mateusz]

It's getting interesting
I checking 10<->40 - its continuity
I checking 2 with ING ON - its live
I plug in bitron and ground 40 - no click
Unpluging bitron and grounding only 2 & 10 pins from car battery - its click
Next grounding only 2 & 10 with same pins in bitron connector - its click
Mount it again on the place - second relay dont click , first relay works fine
something's blocking him, i guess its immo but i can't enter code as you seen on video

[xantia_v6]

I think that you are measuring voltages at the plugs by disconnecting them. Often you need to measure the voltage with everything plugged in, as for example, the injection relays will not be energised unless they and the ECU are both plugged in.

To measure voltages with everything plugged-in, you need to use a needle probe pressed through the insulation of the wire.

[white exec]

I think that you are measuring voltages at the plugs by disconnecting them. Often you need to measure the voltage with everything plugged in, as for example, the injection relays will not be energised unless they and the ECU are both plugged in.

To measure voltages with everything plugged-in, you need to use a needle probe pressed through the insulation of the wire.

That is a thorough way to check, under operational conditions.
Sometimes a voltage can be detected on an 'open ended' cable or connection, but when current is drawn, a bit of resistance (eg at a poor connector pin) can drop the voltage enough to make it disappear, and not operate the device properly. The greater the wattage of the device, the more important it is to have near-zero resistance.

As Mike says, a sharp needle, pushed though a wire's insulation, will allow you to check whether the wire is live or not, and what voltage is there under operating conditions.

[white exec]

It's getting interesting
I checking 10<->40 - its continuity
I checking 2 with ING ON - its live
I plug in bitron and ground 40 - no click
Unpluging bitron and grounding only 2 & 10 pins from car battery - its click
Next grounding only 2 & 10 with same pins in bitron connector - its click
Mount it again on the place - second relay dont click , first relay works fine
something's blocking him, i guess its immo but i can't enter code as you seen on video

The Bitron second relay clicks when pin 2 is +, and 10 is Gnd. Good.
That suggests the second relay is working ok.
Plugged into the car, it isn't clicking.
......That means either pin 2 is not staying at +12,
OR pin 10 isn't being grounded properly.

As Mike suggests, pierce the insulation of the wires going to 2 and 10 on the Bitron, and check whether they go/stay at +12 and 0v.

If necessary, with Bitron and ECU plugged in, check that there is +12 on pin 2, and make a ground connection (from the piercing needle) from the pin 10 wire to Gnd. That should make the second relay click. See whether that happens.

[Mateusz]

Cant make him click
Bitron and Inj Ecu plugged in.
I punctured wires in bitron close to connector.
Tested by light bulb 5W in the circuit
connected (-) from battery and punctured wire 2 - the light is on
connected (-) from battery and punctured wire 10 - no click
connected (+) from battery and punctured wire 2 - no click
connected (+) from battery and punctured wire 10 - no click, the light is on
Checked also with old analog multimeter (its not precise) but power on pin 2 was similar with bitron plugged and unplugged

[white exec]

Cant make him click
Bitron and Inj Ecu plugged in.
I punctured wires in bitron close to connector.
Tested by light bulb 5W in the circuit *****
connected (-) from battery and punctured wire 2 - the light is on OK

connected (-) from battery and punctured wire 10 - no click NO - second relay should close. Just possible it is closing silently, but not likely. *****
connected (+) from battery and punctured wire 2 - no click OK - doing same as switching IGN on *****
connected (+) from battery and punctured wire 10 - no click, the light is on (Not a good test) *****

Checked also with old analog multimeter (its not precise) but power on pin 2 was similar with bitron plugged and unplugged

***** I take it you were not using the 5W bulb in those last three tests. They check would need to be by direct wire, because the 5W bulb would act as a voltage dropper.

From that, it looks as if the second relay (2----10) is not operating.
You could take the relay out, put it on the bench and test:
+12v on pin 2
– on pin 10
when the relay is powered, you should get continuity between pin 1 and pin 9, and pin 11 and pin 9, and pin 1 and pin 11.
See Gabor's circuit for how the relay internals are connected.
You might also be able to open up the Bitron unit, and check for dirty contacts, or mechanical defect.

If the unit is duff, it seems still to be available new, from Citroen...
Part number 1920 3X (if your RP number is 6601→)
Part number 1929 40 (RP number →6600)
(RP number is painted on the front passenger side A-post, between the door hinges).

Would be a good if Mike (xantia_v6) or Paul (citroenxm) could check this part number out, before you go ahead and buy one.

[Mateusz]

Found another bitron from my old 2.5td, its the same model. Plugged in and the same problem.
Does in unplugged bitron connector should be continuity between 2 and 10 pins? I noticed resistance so that could be reason.

[white exec]

Unplugged, resistance between 2 and 10 would be the resistance of the relay coil. Don't know exact figure, but probably between 50 and 200Ω. Multimeter reading will show a high reading one way round, lower the other, due to the series diode.

What was the result of this test?
↓
From that, it looks as if the second relay (2----10) is not operating.
You could take the relay out, put it on the bench and test:
+12v on pin 2
– on pin 10
when the relay is powered, you should get continuity between pin 1 and pin 9, and pin 11 and pin 9, and pin 1 and pin 11.
See Gabor's circuit for how the relay internals are connected.
You might also be able to open up the Bitron unit, and check for dirty contacts, or mechanical defect.

You could also try the same test on your old 2.5 relay (it is exactly the same part, 1920 3X), and compare the two.