My Citroen XM 3.0 PR-Vestige

[White Exec]

If the TPS and its associated ECU is anything like the throttle pedal sensor for Hydractive, then the ECU might need to progressively "learn" the voltages the TPS is ending out, as the car gets driven. Idle is learned almost instantly, but as the throttle gets opened more and more, it will take on board (no pun intended) the voltage range offered. . . . . Unless, of course, it is pre-programmed with idle and full-throttle voltages - although it may use these figures until real-life throttle opening updates them. Whichever way, full functioning might not take place until the car gets driven a bit. Again, just guessing.

Think you are right to look at whether wide throttle should produce a higher voltage (or not). Presumably some documentation should say. Fault finding section of the injection pages??? Also wondering along the same lines as Misha in his last post.

[misha]

Most of the cars needs full tps "learning" procedure but these cars not.
I replaced mine last year and it is just "plug & play".

When you reset ecu,you also reset the whole fuel trim.A simple short drive quickly " re-learns" ecu.Mostly for idling values.
Ecu is pre-programed but "re-learning procedure" just fine tunes the fuel trim and smooth things out.

[Dean]

What happened with pins positions?Why you had to swap places of pins 1&2?
Tps have 3 pins on both....tps side & connector's side.You have donor's car engine wiring.Connector can't be plugged wrongly.What am i missing here?

The donor loom had the TPS plug cut of at some point and a new plug fitted using scotchlock connectors, i cut this off and soldered a new plug on with the wires in the same way as i found them and wrapped it up in original loom tape and ducting. not sure how it ran before but then i dont know this is the issue yet, keeping my fingers crossed it is though!

D

[Dean]

The TPS itself only has 90 degrees of travel and depending on which way its wired it will either increase or decrease resistance/voltage when the spindle is turned, it was wired the wrong way round so as throttle was applied the ECU was seeing the throttle close. This must have been confusing for the ECU.

D

[misha]

..The donor loom had the TPS plug cut of at some point and a new plug fitted using scotchlock connectors, i cut this off and soldered a new plug on with the wires in the same way as i found them and wrapped it up in original loom tape and ducting. not sure how it ran before but then i dont know this is the issue yet, keeping my fingers crossed it is though!

Wiring for tps sensor on 2.0i have all three wires in same green color,i suppose v6 is the same.So....it is pretty easy to mix them up while changing the connector.
About how the car ran like this....i doubt that it was driveable...that's for sure.

[Dean]

it didnt run on petrol when i got it but i suspect i could of mixed them up.

Now to see why the ECU is unhappy with the Crank sensor.

D

[misha]

I would be more worried about that noise when engine is running.Are you sure it's not from hydraulics?

It's also strange that ecu doesn't see crank sensor,and more strange that check engine light is not ON with permanent fault stored.
Since the wiring was allready disturbed i wouldn't exclude the possibility that ecu is the problem on this and not the crank sensor itself.Maybe something was shorted out at previous owner and that killed a component in ecu.

A quick peek inside of an ecu could reveal something.....or not.

[xmexclusive]

Dean/Misha

Nothing strange about the Crank sensor and engine light.
Should read 330 ohms on pins 1 & 2 (test disconnected).
Must also be insulated from earth.
Crank sensor fault is code 31.
Classed as a minor fault.
Does not light the engine fault light.
(Source of info XM 1 no. 1 page 38).

John

[misha]

Interesting....
Being an permanent fault and considering that ecu doesn't see it at all....how come that rpm gauge is working?
Rpm signal is comming from ecu,but according to TDC sensor data.If ecu doesn't see it,what runs rpm gauge?

[Dean]

Thats interesting John, i thought the crank sensor would be too important for engine operation but it would seem not.
Resistance on pin 1+2 is 340ohm the new sensor was slightly higher.

The noise is of concern yes, its not hydraulic and i hope that when i can run the engine up to temperature and it runs well i can identify the problem then, the belts are all about the right tension but the pulleys have been painted, i hope that is the problem but we shall see.

Thanks
D

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