My Citroen XM 3.0 PR-Vestige

[White Exec]

That is quite likely, but interesting that it has lost its markings. Damaged? Value?

[Dean]

I think they come without markings from new Chris, all the replacements i looked at are the same.

More intrigue and befuzzlement this evening. I have in my possession now a green label ecu from a 93 V6, with the code, this is what happened.

Fit ecu, turn ignition on, both red and green lights on keypad (immo fault)
Turn ign off and back on a couple of times, immo goes straight to green with no code entered
Tested for power on front knock sensor, none. No 5v ouput at ecu
Start engine, idle is 550-600rpm from cold the engine should rev up to 1100rpm and settle at 850rpm after a minute or so, engine running rich (smelly) lumpy.
Engine much happier returning to idle with this ecu, when revved the engine settles back to its inappropriate idle speed rather than dropping down below and stuttering before lifting back up to 850rpm like the other ECU does.

Could i have two duff ECU's, are they just too different to swap? do any V6 engines actually get voltage to the front knock sensor.

Interesting

D

[Dean]

Actually, very different indeed, both component count, type and location is very different between the two

This is the original Fenix 3 S111700211 C ECU board, the case is marked with an all white label (BVA/SO2) for auto transmission, the case is moulded Alloy with the name SIEMENS
IMG_3394 by Deanxm, on Flickr
This board looks very 80's to me, but i know jeff all about electrickery

This is the Fenix 3 S101700101 H ECU there are no other markings on it other than the green coloured label. Thinner moulded alloy case with the name Bendix
IMG_3393 by Deanxm, on Flickr
This board looks very modern, it even has closed cell foam insulation on the inside of the ecu lid.

From this i would say ECU's are NOT a mix and match item across the board, even though both these ECU's pre-date the ecu plug pinout changes that came with the MK2

D

[Dieselman]

As long as all the pin-outs are the same, it should work.

[White Exec]

[Dean]

The facts are this.

I am running an earlier 2975cc engine with early style loom (pinouts differ in order and number from MK2 loom)

My ecu has been found tonight to be manufactured after July 94 as the internal case date stamp proves
This ECU runs the engine nicely BUT, No supply voltage to front knock sensor, flickering power supply issue, self wiping fault code memory and suspected ECU control of the ignition timing problem.

Green Label ECU supplied is claimed to come from a 93 model year car
Does not power front knock sensor
Does not control ICV resulting in base idle setting of about 500rpm and stalling when selecting gear
Very rich running, shooting flame from the exhaust when on the over run from being rev'd
Fault codes stay stored
No flickering power supply issue

I am rapidly forming the (misguided?) assumption both ECU's are incorrect for the Loom layout, i need to find a genuine early 92 or earlier ECU to confirm as i am only swapping the ECU and some faults vanish and new ones appear.

Open to other theories?

D

[sdelasal]

Dean - this comment => 'No supply voltage to front knock sensor' - is that 5v supply dedicated to that sensor or shared with other sensors? Is it possible you have a wiring fault where the 5v supply is being grounded in the loom, or thru a duff component? Is the 5v there on the output pin if you open circuit the ecectrical connection to it?
Steve

[Dean]

Hi Steve

No there is no 5v output from either ECU, the UFZ ECU (my original) has a large 5v rail the voltage regulator is soldered to, every sensor that uses 5v is pretty much fed separately from this rail on the board, the two knock sensors have their own dedicated 5v supply through a small SMD Capacitor, then a resistor and out into the loom, on this channel i have 5v going into the SMD Cap and 1.75v out the other side to the resistor, 0v makes it out the other side of the resistor.

The rear sensor has 5v going through the capacitor, resistor and all the way to the sensor via the loom.

Neither ECU's output a reference 5v supply to the front knock sensor, the newly acquired SFZ ecu isn't getting a control signal to the ICV stepper motor either though.

Also the UFZ ECU detects when neutral and drive is selected on the gearbox, the SFZ does not.

Looking for the S6A?? ECU if someone has one to try, im getting convinced my problem is incorrect ECU, they will all run the car just not very well.

Sorry Steve, waffling. There is no 5v either open or closed circuit, no output from multiplug connection on ECU
Supply is not shared for the knock sensors, each has a dedicated 5v supply to pin 2, pin 1 is signal, pin 3 ground
front knock sensor is missing only the 5v reference voltage, has perfect continuity with the track on the ECU board (pin 31) to pin 2 on the front knock sensor plug


D

[misha]

Maybe these guys could help,they are in UK:
https://www.atpelectronics.co.uk/" onclick="window.open(this.href);return false;

[xmexclusive]

Hi Dean

Think you have the ECU ages a bit wrong.
White label very early V6 auto.
Green label is V6 manual.
Yellow label is later (91) V6 auto.
Case code number also need checking as do the index letters.
For each colour code there are a sequence of index letters as each ECU version is modified.

I put a list of these as far as I knew on here about a year ago (PRV V6 12v ecu - tue may 17 2016).
You commented that it was very useful information.

John