My Citroen XM 3.0 PR-Vestige

[sdelasal]

Dean, that's annoying. What's the reference (-ve) point for your measurements? What does the manual assume? It'll be either the chassis ground or an appropriate ecu ground. I remember when working on matthew's car on the throttle sensor that I was getting bizzare voltages dependaing on what I used as a reference point. If the grounds are all good then there should be minimal difference - but just asking...

[misha]

I'm still standing behind my advice that ecu is bad.Like i allready said,i had similiar situation when i didn't getting proper reference voltage for TPS from ecu.
Try with a good known ecu.
Ecu "re-learning" should be present from s2 and newer engine management.

[Dean]

It would be interesting to now try the manual ECU and see if it works..........but i want to enjoy using it a bit now Misha!

Reference voltage is slightly up by .1v and reads as 5.1v grounded either to the Sensors own ground wire, the chassis or battery terminal Steve.

Test drive fine, she is spot on now, idle is correct, pulls well, and i can drive at 1400rpm no worries, perfectly smooth with a smooth transition over the fuel cutoff and trailing throttle/accelerating. Perfect AT LAST!

So i have got it to work perfectly but by setting the signal voltages to nothing like Citroen says and wiring it nothing like Citroen says........................of course!

Idle voltage .86v / WOT 2.95v

D

[misha]

Here is my thread about bad ecu producing a bad TPS reference voltage:
viewtopic.php?f=4&t=5390" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;:

What happens if you disconnect TPS?It should go into limp mode relying on Map & o2 sensor.Did you tried it?

[Dean]

Will read through in a minute.

Yes i did disconnect it, when disconnected i know the ecu selects Mid throttle position and a 2.3v signal is shown via the Lexia live data screen.
In practice when i tried it today in the pissing rain by the side of the road, all that happens when its disconnected is the idle speed goes up and up and up and would be impossible to drive, when it reached about 1600rpm i just plugged it back in, closed the bonnet and carried on as i just needed to use the car and had no choice.

D

[White Exec]

SFAIU, the TPS is just a potentiometer, which allows a sweep over part of its track (depending on how you 'clock' it).
If Citroen require a WOT figure of x volts, and you can't achieve that in practice, then it can be achieved by simply supplying the top end of the pot with a slightly higher voltage. Not worth trying? The WOT figure you quoted was just about hanging on the margin of what the ECU was looking for.

Also, could also be an issue of the pot not being used over a sufficient length of its track . . . i.e. an issue of mechanical linkage . . . but presumably something you might not much control over.

The supply voltage would be far easier to manipulate, I guess.

[misha]

I vote for a bad ecu.It simply doesn't leave you any choices.You allready tried it all.

[Dean]

............Including a new ECU, the new ECU was worse than the existing one but probably due to the incorrectly wired TPS.

It runs and drives perfectly now though even though the TPS voltages are out of spec and i have no 5v reference voltage to the front knock sensor.

Im trying to find other peoples Lexia live data screen shots to see what their TPS voltages are though.

D

[Dean]

Here is a link to Matthews V6 saga showing Lexia live data pages
viewtopic.php?f=19&t=6664&start=330" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;
viewtopic.php?f=19&t=6664&start=260" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;
His output signal voltage from the TPS are miles out of spec given most are at idle, also his ECU never displays 'IDLE' status meaning it's not cutting fuel on a trailing throttle above 1400rpm.
This is no use to me because his reading are all way out from what Citroen says they should be, i want to find someone who has a Pre 1994 petrol XM and see what their TPS says.

My 2.0 used to only show 'IDLE' and 'MID' as throttle position, not sure what the output voltages were as i never had cause to look properly at it.

D

[Dean]

well they are at the second link, the first looks ok actually if he is fiddling with the throttle position, it could be he has a manual ECU fitted and it does not see idle in order to not use the fuel cutoff feature.

The same as the manual ECU only ever see's the gear selection as 'Drive' when fitted to an auto car no matter what gear you select.

D